ENW Fundamentals of a Well-Built SAN White Paper

8/8/2019 ENW Fundamentals of a Well-Built SAN White Paper

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Fundamentals of a Well-Built SANWhite paper

Introduction......................................................................................................................................... 2Executive summary............................................................................................................................... 2

Anatomy of a SAN .............................................................................................................................. 3 The advantages of iSCSI SANs ............................................................................................................. 3Core features of HP LeftHand SANs ....................................................................................................... 3

True clustering ................................................................................................................................. 4

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Storage virtualization ....................................................................................................................... Reliability with network RAID............................................................................................................. Continuous data availability.............................................................................................................. Scalable capacity and performance ................................................................................................... Easing administration overhead......................................................................................................... Enhanced data services ....................................................................................................................

Based on HP server technology ............................................................................................................. Accelerated technology refresh rate ................................................................................................... Investment protection ........................................................................................................................ Lower administration overhead .......................................................................................................... HP Services .....................................................................................................................................

Scalable performance .......................................................................................................................... Scalability by design ........................................................................................................................ Limitations of traditional architectures ................................................................................................. Objective scalability measures........................................................................................................... Flexible scalability models................................................................................................................. Scaling with tiered storage................................................................................................................

High availability.................................................................................................................................. Synchronous replication and disaster recovery with multi-site SANs......................................................

Reliability by design........................................................................................................................... Building reliability from the ground up ..............................................................................................

Extreme performance ......................................................................................................................... Performance through parallelism...................................................................................................... Increasing parallelism and performance with MPIO DSM ................................................................... Increasing bandwidth dramatically................................................................................................... Protecting investments.....................................................................................................................

Conclusion........................................................................................................................................ For more information..........................................................................................................................


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Introduction

Next to its people, data is a companys most valuable asset. Businesses of every size rely heavily ondata that is at once increasingly complex and increasingly regulated. Government regulations incountries around the world dictate how financial, customer, personnel, and health-related informationis stored, maintained, and retained.

Central data storage and management help organizations achieve compliance with this mountain of

requirements, and help to ensure that business-critical data will be available when users need it.Storage area networks, or SANs, are common solutions for businesses seeking to simplify storage.Unlike direct attach storage (DAS), which creates disparate, random islands of information, SANscentralize data storage. Disaster recovery solutionsa necessity in todays worldare easier toimplement on SANs, and the stored data is easier to manage than in a DAS environment.

A company that leverages server virtualization for high availability and disaster recovery has evenmore reason to deploy a SANand not just any SAN. Virtualized environments need shared storageto take full advantage of the shared infrastructure. When both server and storage are protected, thesolution is complete.

Although Fibre Channel SANs are an option for large enterprises, these storage solutions tend to beexpensive and limited in their flexibility. Compact and cost-effective, iSCSI SANs are a better fit for

many businesses. HP LeftHand iSCSI SAN solutions are built in a way thats fundamentally different.Built from the ground up to be flexible, scalable, and highly available, HP LeftHand P4000 SANsdeliver all of the features of enterprise storage and are an excellent fit for disaster recovery, businesscontinuity, and virtualized storage solutions.

Executive summary

Your businesss increasing reliance on data calls for a well-designed and well-built data storagesystem. Agile, easy to deploy, and intuitive to manage, HP LeftHand P4000 SAN Solutions provideall of the functions that organizations expect to see in a Fibre Channel SANat an affordable pricepoint that makes centralized storage an economical option even for small- and medium-sized

businesses. Because HP LeftHand SANs are built with a superior architecture, they are more scalableand offer higher availability, more reliability, and higher performance than other iSCSI SANproducts.

HP LeftHand SANs are based on iSCSI technologySCSI over standard Internet protocols (IP). Thisallows companies to use the standard iSCSI drivers that accompany server operating systems toaccess storage over standard IP networks.

HP LeftHand SANs use a process called true clustering. True clustering means that every storagesystem in a cluster participates equally in sharing both the clusters workload and storage capacity.The cluster manages itself. With true clustering, organizations can administer a single entity whileconfiguring virtual volumes and per-volume network RAID levels. They can also take snapshots, makeremote copies, scale the cluster, and even take storage systems down for upgrades or maintenance

all without affecting data availability.

HP LeftHand SANs deliver the enterprise storage management features that companies expect of FibreChannel SANs. However, the similarity ends there. The purpose of this white paper is to describe thebenefits of a clustered architecture in comparison with traditional controller-based architectures, andto discuss the technology that makes HP LeftHand SANs better by design.

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Figure 1: HP LeftHand P4000 SANs are built using enterprise-class HP servers. The physical blocks in the SANcorrespondingto virtual volumesare distributed evenly across the cluster.

True clustering

P4000 SANs provide true, n-way clustered storage, not a traditional two-way active/active or

active/standby configuration. True clustered storage means that a set of storage systems is managedand scaled as a single entity, with all of the clusters resources available to respond to requests. Asthe cluster is expanded, the resources available to handle requests increase as wellalleviating theproblem of a controller bottleneck, which is commonplace when traditional SANs are scaled.

Storage virtualization

True clustering creates a virtual pool of storage, spreading the storage for its virtual volumes evenlyacross all storage systems in the cluster. Storage can be reserved at the time that the virtual volumesare createdor, through thin provisioning, it can be allocated only as disk blocks are actuallyneeded.

HP LeftHand SANs virtualize every volume across all the storage systems in a clusternot within eachstorage system, as do traditional Fibre Channel SANs. The sharing of storage across the entire clusterresults helps increase performance and storage utilization; in addition, it helps decrease managementcosts and complexities as clusters are scaled.

Reliability with network RAID

The reliability of HP LeftHand SANs begins with RAID storage on each storage system. It is thenenhanced with network RAID, which replicates each block across the storage cluster up to four times.

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When a virtual volume is populated, its data blocks are striped and replicated across the clustersstorage systems so that the entire cluster participates in the storage of every virtual volume.

Continuous data availability

Network RAID contributes to high availability, helping to ensure that the loss of a single storagesystem does not result in data loss. If a server fails to the point where it must be taken offline forrepair, network RAID keeps the single server failure from resulting in loss of data availability. Whenthe server is replaced, or repaired and brought back online, the SAN automatically brings the storagenodes data blocks up to date with the rest of the cluster.

The more storage nodes there are in a cluster, the less the failure of a single storage system can affectperformance. A traditional active/active dual-controller SAN product can suffer a 50% performancedecrease in the event of a controller loss. With P4000 SANs, the failure of a storage node affectsperformance by, at most, a percentage equal to the proportion of the cluster that the storage systemrepresents.

Scalable capacity and performance

As a cluster becomes full, storage capacity can be increased by adding storage nodes. Trueclustering enables considerable scalability. As new storage nodes are configured, the cluster

automatically readjusts its block allocation so that the allocated storage and the workload are onceagain distributed across the cluster. This procedure immediately scales the clusters performance bybringing incremental network CPU, memory, cache, RAID controller, and disk resources to the cluster.

Easing administration overhead

All storage clusters are managed through a single, intuitive centralized management console (CMC).The ability to treat a storage cluster as a single entityrather than a set of discrete storage deviceseases administration costs and changes the cost model from one in which storage must be plannedand purchased upfront to one in which it can be purchased as needed.

Enhanced data services

In traditional SANs, enhanced data services are typically add-on features. With HP LeftHand SANs,enhanced data services are included at no additional charge. Synchronous replication keeps datahighly available within a cluster, even if that cluster is geographically separated between sites in aLAN or MAN. Remote copy provides disaster recovery for multiple clusters and sites from a singleinterface, and failover and failback are automated features. The unique allocate-on-write thinprovisioning provides the ability to create volumes without dedicating physical storage to them.Snapshots are space-efficient because they are thinly provisioned.

Based on HP server technology

P4000 SANs use cost-effective, reliable, and high-performance HP server hardware. The resultingstorage cluster offers greater performance and reliability than many purpose-built storage devices.Basing storage systems on enterprise-class server hardware from HP adds to the superiority ofHP LeftHand SANs in a number of ways.

Accelerated technology refresh rate

The fast server technology refresh rate brings the latest technology to HP LeftHand SANs quickly. Inthe storage industry, products tend to be refreshed every 24 to 36 months, but the server industrypushes technology into customers hands on more of a 9- to 12-month cycle. In other words, the

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benefits of higher-performance, higher-capacity drives, and the latest networking technology are oftenavailable with HP serversand thus HP LeftHand SANslong before they are available withtraditional SANs.

Investment protection

Using HP servers offers unprecedented investment protection for organizations, because they canbuild their entire server and storage infrastructure from the same basic components. They canrepurpose existing storage servers as application servers and, using the HP LeftHand P4000 VirtualSAN Appliance (HP P4000 VSA) Software, provide SAN storage on them as well.

Lower administration overhead

Leveraging HP server technology means having a more homogeneous environment to support, whichleads to greater staff efficiency. Purchasing HP LeftHand SANs often brings more HP technology intothe many data centers already using HP servers. This allows organizations to build upon their existinginfrastructure and knowledge, rather than investing in an entirely new, parallel infrastructure forstoragewith all of the associated training and management costs.

HP Services

HP LeftHand SANs are supported by global, world-class enterprise-support services. This can be asignificant advantage for data centers already engaged with HP. Companies may already havespares on site; they may already know their support technician, and the technician may already bebadged for the site and familiar with its best practices. The size and skill set of the availablehardware support from HP also helps organizations compete.

Scalable performance

Scalability means that adding more resources to a system results in a commensurate increase in thesystems ability to perform work. HP LeftHand SANs use true clustering to deliver a SAN that scalesboth storage capacity and performance in a linear manner. Scaling a cluster with additional storage

systems supports growth by scaling existing volumes, adding new volumes, and supporting moreservers (Figure 2).

Scalability by design

HP LeftHand SANs are designed to deliver massive scalability. Unlike other clustered storageproducts, P4000 SANs have no built-in limit on the number of storage systems per cluster. Becausetrue clustering allows them to scale performance and capacity linearly, HP LeftHand SANs differ fromtraditional Fibre Channel SAN products.

HP LeftHand SANs are based on HP ProLiant servers, each of which has its own disk drives, RAIDcontroller, cache, memory, CPU, and networking resources. Thus, each time a new storage system is

added to a cluster, the clusters processing capacity increases in lock step with its storage capacity.The SANs linear scalability derives from the fact that the ratio of processing resources to disk storageis constant.

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Figure 2: HP LeftHand SANs use true clustering to deliver linear scalability that can support more storage capacity andperformance as the cluster grows.

Limitations of traditional architectures

Compare this scalability model to the traditional controller/disk tray architecture that is behind mostFibre Channel SANs and some NAS appliances (Figure 3). These systems use either an active/activeor an active/standby pair of processors, and scalability is achieved by adding more disk trays to theconfiguration as more capacity is needed. Using this model, the ratio of processing power to diskcapacity decreases each time a new disk tray is added to the configuration. This causes performance

to increase to the point where the controllers and the Fibre Channel interconnect become abottleneck; performance then levels off or even declines. At that point, customers must either upgradeto higher-power controllers or add new storage systems. Either action can result in significant amountsof downtime.

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Figure 3: A traditional SAN architecture scales by adding more disk trays to the configuration.

Objective scalability measures

ESG Lab, part of the Enterprise Strategy Group, measured scalability of HP LeftHand SANs of varying

sizes, and summarized the results in a July 2007 report1. The test cluster consisted of an HP LeftHandSAN configured with up to 30 HP ProLiant DL320 Servers. Each server was configured with 12300GB, 15k rpm serial-attached SCSI (SAS) drives, yielding a total of 3.6TB of storage per server.ESG used the IOMeter benchmark to drive a simulated online transaction processing workloadconsisting of 60% read and 40% write operations, using 8KB blocks. Scalability was nearly linearfrom five to 30 storage systems, and the 30-server, 108TB cluster was able to sustain almost50,000 input/output operations per second (IOPS).

HP LeftHand SANs allow organizations to build clusters whose characteristics are tuned for theapplications they support, scaling each cluster as needed. Many organizations deploy their firstopen iSCSI SAN to support specific applications such as Microsoft Exchange Server, VMwareInfrastructure 3, Microsoft SQL Server, and network file sharing. As they begin to see the benefits of

HP LeftHand technology first hand, they scale their cluster to support more and more applications(Figure 4). As these applications become more diverse in their storage requirements, it often makessense to create a new cluster with a different type of storage system as its basis. Both clusters canscale independently, and logical volumes can be moved between clusters with no interruption inservice. This makes scaling with tiered storage easy and straightforward.

1 LeftHand Networks 100 TB Enterprise SAN.

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Figure 4: Network RAID level 1 stripes and replicates a logical volumes data across the cluster.

Flexible scalability models

HP LeftHand SANs scale capacity as well as performance. Organizations can increase the storagecapacity of a cluster by adding new storage systems, and they can even scale clusters with non-identical storage systems. Scaling a cluster to 100 storage systems is as simple as scaling to two. Inaddition to scaling the size of a cluster, companies can create multiple clusters because the cluster ismanaged as a single unit.

Multiple SANs are configured in a single management group by the centralized management console(CMC), which provides a single, intuitive graphical user interface (GUI) to manage them. Logicalvolumes can be copied between clusters with a simple click of the mouse. Given the fact thatmanagement groups can span geographical distances, remote copy works as simply and easily as alocal copy does between clusters.

Scaling with tiered storageDifferent types of disk drives have different performance characteristics, and these characteristicsaffect storage system performance and thus overall SAN performance. SAS and SCSI drives tend tohave high rotational speeds and low seek times, resulting in low I/O latency and therefore highinput/output operations per second (IOPS). Storage systems using SAS drives excel in supportingtransactional applications such as databases and Microsoft Exchange servers. Serial ATA (SATA)drives tend to have lower rotational speeds and higher latency, but much higher capacity for the pricethan SAS and SCSI drives. Clusters built around these storage systems are more cost-effective forapplications that demand high capacity, such as streaming media and general file storage.

High availabilityAvailability is about keeping data online and available at all times, an attribute that is typicallyattempted by using redundant components. What happens if multiple components fail within a unit, orthe entire unit becomes unavailable?

The HP LeftHand P4000 SAN has redundant components such as redundant power supplies andhardware RAID 5, 6, and 10. But, to achieve true high availability, volumes must remain onlinewhether a drive fails or the entire unit becomes unavailable. Network RAID provides this capability atno extra charge.

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Network RAID levels are assigned on a per-volume basis so that availability can be configured basedon the needs of individual applications and their data. This allows organizations to incur the cost ofredundant storage only for logical volumes that require it.

HP LeftHand SANs support striping plus network RAID replication levels 0, 2, 3, and 4, whichcorrespond to replicating each block up to four times. The most commonly configured network RAIDlevel, level 2, stripes and replicates blocks so that two copies of each block reside on the cluster(Figure 4). Using this configuration, the logical volume continues to be available despite the failure ofa single storage node or the failure of two non-consecutive storage nodes. Compare this to products

that stripe without replication: the more servers in a cluster, the lower the availabilityand the loss ofa single storage system means that all storage is lost.

In HP LeftHand SANs, clusters manage data layout and replication themselves so that failover isautomatic and so is failback. If a storage system fails and is later brought back online, the clustermanages the process of restoring the repaired servers data to the current level. Likewise, networkRAID level is a property of a logical volume that can be changed at any time. If the network RAIDlevel is changed, the cluster manages the process of increasing or reducing the replication level ofdata for the logical volume as required.

Synchronous replication and disaster recovery with multi-site SANs

The availability properties of network RAID mean that functionality such as synchronous replicationand disaster recovery is built into the solution. This simplifies administration, helps to protect data, andreduces costs compared to traditional SANs.

Volumes stored with network RAID level 2 have blocks striped across every other storage system, withreplicas stored across the rest. Logical volumes continue to be available even if half the systems in thecluster fail.

Synchronous replication to provide multi-site high availability can be implemented simply by placinghalf the storage systems in one location and the rest in another. Whether the alternate location is adifferent closet in the same building, another building on the same campus, or a data center faraway, blocks are synchronously replicated across the two sites, and an entire site can fail withoutmaking any data unavailable (Figure 5).

When the failed site comes back online, its storage systems automatically obtain any changed blocksso that failback is automatic and transparent. With traditional SANs, this process can be time-consuming and error-prone, and it can require application downtime.

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Figure 5: Placing alternate storage systems in different, alternate locations enables synchronous replication and disasterrecovery as natural side effects of HP LeftHand SAN storage.

Reliability by design

Reliability is about protecting against data loss, which is a considerable proposition given the forwardmarch of disk technology. Disk reliability is typically expressed in terms of bit error rate (BER), whichmeans that disks may fail as a function of the amount of data read or written. As disk technologyallows drives to contain more data, they are more likely to fail when read from beginning to end; thisis exactly what happens during a RAID array rebuild after a single-disk failure.

The upward trend in disk sizes means that the dreaded second-disk failure that incapacitates a RAID 5array is becoming more likely as disk sizes increase. Indeed, the chance of a second disk failurewhile rebuilding a 9TB RAID array of SATA disk drives is nearly 10%greater than the probability ofa dual controller failure in a traditional SAN. RAID 5 by itself is no longer sufficient. The reliability bydesign of the HP LeftHand SAN allows organizations to configure logical volumes and clusters toprovide higher reliability levels.

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Building reliability from the ground up

Reliability is built into every HP LeftHand SAN, from the choice of storage nodes to the additionalfeatures that help organizations better manage their data.

Hardware featuresEvery component in an HP LeftHand SAN includes dual power supplies,network interface cards (NICs), environmental monitoring, and a battery-backed-up write cache.

Choice of drivesThe HP LeftHand SAN offers storage options that allow customers to choose thecombination of performance, capacity, and reliability that best suits their applications. Enterprise-class SAS and SATA drives offer reliability levels equivalent to the Fibre Channel drives found intraditional SANs, with a BER of 1/1016. Where capacity and price are more important than thislevel of reliability, SATA drives can deliver a BER of 1/1014.

Hardware and network RAIDEach storage system has built-in hardware RAID and battery-backed-up write cache, both of which contribute to reliability and data protection. Depending on the systemand customer requirements, hardware RAID levels 5, 6, and10 can be configured on each storagesystem and then combined with network RAID levels to maximize availability.

Proactive self-healingJust like traditional Fibre Channel SANs, HP LeftHand SANs monitor storagesystems for marginal environmental or drive conditions, allowing an HP LeftHand SAN to respondwith proactive support services, repairing potential faults before they result in an actual failure.Each storage system is constantly scrubbing its storage to re-map bad blocks and restore data froma storage system that has an intact replica.

Geographic failoverMany organizations view the potential loss of data and application downtimedue to the failure of an entire data center as unacceptable. Network RAID allows for synchronousreplication and geographic failover so that business can continue without interruption. As discussedin the section, Synchronous replication and disaster recovery with multi-site SANs, synchronousreplication is integrated into the superior architecture of HP LeftHand SANs. Whats more,organizations can purchase an HP P4300 SAS Starter SAN for the price that some vendors chargefor their remote replication software alone. And, unlike the competitions remote replicationsoftware, failover and failback are not applicable to a HP LeftHand SAN because storage volumesremain online and accessible throughout a site failure.

Space-efficient snapshotsEvery organization knows that there is no substitute for stable, offlinetape backups. HP LeftHand SANs support space-efficient snapshots where only the metadatanotthe blocks themselvesis copied to create the snapshot. Space efficiency means that the storagesystem does not have to reserve an amount of storage for the snapshot equivalent to the size of thevolume itself. Space efficiency results in significant savings compared to traditional SANs.

Scheduled snapshots can be coordinated with application software so that the snapshot representsa stable point-in-time copy of application data. In contrast to traditional SANs, snapshots inHP LeftHand SANs can be mounted and written to by the backup software.

Snapshots may also be created manually and used to create temporary environments for developersand administrators. Software upgrades and patches, for example, can be applied and tested to avolume snapshot and tested on a real server or in a virtual machine before they are put intoproduction. Costs for these snapshots are low because an equal amount of additional storage does

not have to be available in order for the snapshot to be taken. Remote copy and asynchronous replicationThe snapshot mechanism in an HP LeftHand SAN

forms the basis for remote copy and asynchronous replication capabilities. Snapshots contain anidentifier that ensures uniqueness within a management group. Snapshots can be copied betweenclusters, promoted to be actual volumes, and then mounted and used. When clusters aregeographically separated, a local copy becomes a remote copythere is no difference.

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Consider an organization with data centers in Seattle and San Francisco, with New York acting asa central data repository for backups or as a disaster recovery site (Figure 6). Snapshots can becreated in Seattle and San Francisco, copied to New York, and then promoted to be fullypopulated volumes. Servers C and D, the users of the promoted snapshots, could represent hotstandby servers for disaster-recovery purposes, or they could be used to handle tape backup of thecopied volumes.

Figure 6: Remote copy is based on the snapshot mechanism, and it can be used for disaster-recovery and remote-archivingpurposes.

HP LeftHand SANs support scheduled snapshots and remote copies. Used in combination, these twocapabilities provide asynchronous replication, where batches of data representing the differencebetween two snapshots are created and transferred between sites on a periodic basis.

Reliability is about protecting against data loss every step of the way, from establishing a per-serverreliability baseline to supporting geographic failover and failback capabilities. HP LeftHand SANsprovide flexible reliability at a price point that makes them superior to traditional SANs.

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Extreme performance

The disk spindles performance characteristics ultimately drive disk storage system performance. Onechallenge facing vendors of storage systems is how to extract the most performance from them.

In contrast with traditional SANs, HP LeftHand SANs excel at extracting top performance from storagesystems. Companies that use HP LeftHand SANs experience the high performance and capacity of thelatest disk drivesstandard in the HP ProLiant servers on which LeftHand SANs are basedlong

before those drives are available in traditional SAN architectures. In addition, HP LeftHand SANsleverage the underlying hardware to extract an uncommon level of performance from the hardwareitself.

Performance through parallelism

Most SANs increase storage system performance through parallelism. HP LeftHand SANs alloworganizations to tune the level of parallel operations in their cluster to achieve required performancelevels.

Performance begins with RAID storage on each storage system, which uses parallel disk operations todeliver high I/O bandwidth. Even though RAID 5 is the default configuration, higher and lower RAIDlevels can be configured to adjust both performance and protection. For example, RAID 10 can beconfigured for higher performance requirements, and RAID 6 can be configured to protect againstmultiple drive failures.

A level above RAID on the individual storage systems, the cluster itself contributes to performance bystriping dataregardless of network RAID levelacross the entire cluster. Just as RAID on the storagesystems delivers the performance of disk drives working in parallel, network RAID on the cluster itselfdelivers the performance of multiple RAID arrays delivering data in parallel. Striping across multiplestorage systems is managed by the cluster itself, so administrators can manage only a single entityrather than a set of individual storage systems.

Compared to traditional SANs, where the controllers themselves become a bottleneck as more disktrays are added to a system, HP LeftHand SAN performance grows as storage capacity grows. This is

because each time a new set of disks are added to the cluster, they are supported by an additionalset of resources, including:

CPU and main memory for managing storage, I/O, and the cluster Hardware RAID controller per storage systemAdditional battery-backed-up storage for each storage systemAdditional network interfaces that can operate in parallelIncreasing parallelism and performance with MPIO DSM

By default, an HP LeftHand SAN load-balances initial login requests from client iSCSI drivers acrossthe storage system, and then processes all subsequent requests from that client through a single

storage system. The storage system redirects each client request to the server owning the desiredblock, and then redirects the response back to the client. Although this approach results in excellentscalability, it is not as scalable as the performance that can be achieved with the HP LeftHand device-specific module (DSM) for the Microsoft Windows Multipath I/O (MPIO) iSCSI driver.

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The MPIO DSM contains intelligence on the layout algorithms for the storage cluster. It can thuscalculate the location of any block in any virtual volume. Knowing which server contains the desiredblock allows the iSCSI driver to contact the storage system that owns the block directly, without theredirection used by the standard load-balancing approach. Figure 7 illustrates a redirected loginsequence, the SCSI mode sense command that loads the cluster-specific information into the driver,and the separate I/O path that the driver establishes to each server in the cluster.

Figure 7: The HP LeftHand SANs device-specific module for the Microsoft MPIO driver (MPIO DSM) increases performance byestablishing parallel I/O pathsone to each storage system in the cluster.

The MPIO DSM provides the most benefit with sequential I/O. Performance scalability for standardload-balancing is excellent. However, as the volume of data increases, the load that redirection

imposes on the network increases as well. MPIO DSM eliminates the additional data movement andallows data to stream directly from storage systems to the client systems. Where the benefits of largerclusters for standard load-balancing begin to diminish, the MPIO DSM configuration allowsperformance to continue to climb significantly higher as storage systems are added to the cluster.

Increasing bandwidth dramatically

Most storage systems are limited in bandwidth. In traditional SANs, once storage capacity isincreased to the point where the systems controllers can no longer provide increased bandwidthalong with increased capacity, customers either must upgrade controllers or purchase additionalstorage systems. Multiple traditional storage systems add not only cost but also complexity. They alsoneed to be managed individually with volumes statically allocated to each system, resulting in

fragmentation. In contrast, a storage cluster can virtualize storage across the entire system.

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Protecting investments

Investments in HP LeftHand SANs continue to be protected through the transition to 10-Gb/s Ethernet(10GbE). Using standard, enterprise-class x86-architecture servers means using standard PCI Expressperipherals. Customers can upgrade existing clusters in the field with standard 10GbE interfaces.Redundancy built into the underlying platform allows them to upgrade to a live cluster withoutimpacting data availability.

Unlike traditional SANs, each storage system in a cluster contributes to performance by delivering

data in parallel. So deploying a cluster with 10GbE provides improved throughput, which is thenenhanced further when that throughput is multiplied by the number of storage systems in the cluster.

Conclusion

Every SAN is built from a combination of software, hardware, and services, and in this respect iSCSISANs from HP are no different from any other SAN. But thats where the similarity ends. HP LeftHandSANs use distributed, clustered technology to deliver all of the functionality expected of a storagearea network. They add the advantage of linear scalability, high availability, per-logical-volumeconfigured reliability, and throughput of 10-Gb/s per node that is aggregated between all nodes in acluster. Better by design, HP LeftHand P4000 SANs deliver functionality including synchronous

replication, asynchronous replication, and remote copy. These are built-in features of a superiorarchitecturenot an add-on option that can cost as much as an entire SAN.

With true clustering, HP LeftHand SANs can virtualize storage across all storage systems in a clusterand even between clusters in the same management group. True clustering allows organizations totreat a cluster as a single entity whose resources can be scaled and configured as needed. This helpsdeliver the unique combination of performance and reliability that each application in a data centerrequires.

For more information

For more information on HP LeftHand iSCSI SANs, visit www.hp.com/go/P4000.

Technology for better business outcomes Copyright 2009 Hewlett-Packard Development Company, L.P. The informationcontained herein is subject to change without notice. The only warranties for HPproducts and services are set forth in the express warranty statementsaccompanying such products and services. Nothing herein should be construed asconstituting an additional warranty. HP shall not be liable for technical or editorialerrors or omissions contained herein.

Microsoft and Windows are U.S. registered trademarks of Microsoft Corporation.

4AA2-5616ENW, June 2009
http://www.hp.com/go/P4000http://www.hp.com/go/P4000

ENW Fundamentals of a Well-Built SAN White Paper

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