© 2006 EMC Corporation. All rights reserved. Direct Attached Storage (DAS) Module 3.1
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
© 2006 EMC Corporation. All rights reserved.
Direct Attached Storage (DAS)Direct Attached Storage (DAS)
Module 3.1
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 2
Direct Attached Storage (DAS)
After completing this module you will be able to:
Discuss the benefits of DAS based storage strategy
Describe the elements of DAS
Describe the connectivity options for DAS
Discuss DAS management considerations
Identify the best environments for DAS solutions
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 3
What is DAS?
Internal External Direct Connect
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 4
DAS Benefits
Ideal for local data provisioning
Quick deployment for small environments
Simple to deploy in simple configurations
Reliability
Low capital expense
Low complexity
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 5
Physical Elements of DAS
CPU
Motherboard
Clustered group of processors
Processor cards
Complete system
Internal
External
Hard disk(s)
CD-ROM drive
Optical drive
Removable media
Tape devices/tape library
RAID/intelligent array(s)
Portable media drives
Connectivity
Storage
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 6
DAS Connectivity
Block-Level Access Protocols:
ATA (IDE) and SATA– Primarily for internal bus
SCSI– Parallel (primarily for internal bus)– Serial (external bus)
Buss and Tag – Primarily for external mainframe– Precursor to ESCON and FICON
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 7
DAS Connectivity: Internal
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 8
Internal DAS Connectivity Examples
Parallel Connectivity Cables
34-wire floppy cable
80-wire IDE cable
50-wire SCSI-2 cable
Serial ATA cable
Serial Connectivity Cable
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 9
DAS Connectivity: External
Host Storage Device
External DAS
HBAHBA
Example of an external connectivity cable
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 10
DAS Management: Internal
Host provides:– Disk partitioning (Volume management)
– File system layout
– Data addressing
Direct Attached Storage managed individually through the server and the OS
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 11
DAS Management: External
Array based management
Availability – multi-path I/O
Lower TCO for managing data and storage Infrastructure
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 12
DAS Performance Considerations
Factors to be considered for DAS performance:
• Hard disks
• Memory cache
• Virtual memory (paging)
• Storage controllers• Protocol supported (e.g. SCSI, FireWire, USB, etc.)
• RAID level
• Bus
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 13
Internal DAS Application Example
Hard Drive
40 Pin Ribbon Cable
Motherboard
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 14
External DAS Application Example
ESCON HBACable for
external DAS connectivity
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 15
DAS Challenges
Hosts must be directly connected
Data availability
Data slowdowns possible– CPU congestion, caching, multi-pathing
Scalability is limited– Number of connectivity ports to hosts
– Number of addressable disks
– Distance limitations
Downtime required for maintenance
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 16
Module Summary
Key points covered in this module:
DAS can be:– An integrated part of the host computer
– Directly connected to a single server
DAS is made up of a CPU, connectivity, and storage devices – There are several options within each of these categories
DAS connectivity uses block-level access protocols
© 2006 EMC Corporation. All rights reserved. Direct Attached Storage - 17
Check Your Knowledge
What are the physical elements of DAS?
Give an example of when DAS is a good solution.
Describe internal DAS connectivity.
Describe external DAS connectivity.
What are some areas that you need to consider as part of DAS management?
Related Documents
