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Usage Example of VMware vSphere Space
Reclamation with IBM® System Storage® DS8880
®
This document can be found on the IBM Intranet, http://w3.ibm.com/support/techdocs
on IBM PartnerWorld®, http://partners.boulder.ibm.com
and on the Internet, http://www.ibm.com/support/techdocs
Search for document number TD106413 under the category of “White papers”.
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Disclaimer
This document reflects the authors’ experience from testing the described configurations.
It is presented “As-Is” and IBM® does not assume responsibility for the statements expressed herein.
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Notices and Trademarks ............................................................................................................................... 2
1. Usage Example of VMware vSphere Space Reclamation with IBM System Storage DS8880 ............... 4
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1. Usage Example of VMware vSphere Space Reclamation with IBM
System Storage DS8880
This technical document shows how allocated storage capacity on IBM System Storage DS8880
thinly provisioned Extent Space Efficient (ESE) volume which has already been logically deleted
from the corresponding VMware datastore can be reclaimed again from the VMware ESXi host
by invoking a SCSI UNMAP command as a VMware vSphere Storage APIs for Array Integration
(VAAI) primitive for thin provisioning which is newly supported by IBM System Storage DS8880
R8.2.3 and later.
Our usage example shows a manual space reclamation by a VMware administrator for thinly
provisioned storage which is supported with ESXi 5.5 and 6.0. With VMware ESXi 6.5 and
VMFS6 datastores support for automatic unmap was re-introduced. This automatic unmap runs
asynchronously on a scheduled basis with priority levels that can be set per VMFS datastore.
To illustrate the manual space reclamation function from an ESXi 6.0 host via the SCSI UNMAP
command we cloned an existing virtual machine into a VMware datastore created on a thinly
provisioned ESE volume, deleted the cloned VM again, reclaimed the space from the ESXi host
and checked the corresponding decrease in the allocated storage capacity for the ESE volume.
The following sections show the detailled configuration and steps we performed to illustrate
the new DS8880 space reclamation support for VMware.
1.1 DS8880 Configuration
The following DS8880 DS Command Line Interface (CLI) session outputs show our used DS8880
logical storage configuration.
Verifying that the DS8880 machine is on R8.2.3 or later code level to support the SCSI UNMAP
command:
dscli> lsserver -l
Date/Time: 01 August 2017 15:30:29 CEST IBM DSCLI Version: 7.8.20.280 DS: -
ID Image ID Image Name Power Control SFI State LIC Version OS Version Bundle Version
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Listing the standard (thick) volume 0x1000 and thinly provisioned (ESE) volume 0x1100 we used for our VMware datastores: dscli> lsfbvol -l 1000 1100
Date/Time: 01 August 2017 15:27:48 CEST IBM DSCLI Version: 7.8.20.280 DS: IBM.2107-75GNC81
Name ID accstate datastate configstate deviceMTM datatype extpool sam captype cap (2^30B) cap (10^9B) cap (blocks) volgrp
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sam ESE
repcapalloc -
eam managed
reqcap (blocks) 838860800
realextents 39
virtualextents 41
realcap (MiB) 624
migrating 0
migratingcap (MiB) 0
perfgrp PG0
migratingfrom -
resgrp RG0
tierassignstatus -
tierassignerror -
tierassignorder -
tierassigntarget -
%tierassigned 0
etmonpauseremain -
etmonitorreset unknown
GUID 6005076307FFD7690000000000001100
1.2 ESXi Host Configuration
The following ESXi host command line interface session outputs show our ESXi host storage
configuration.
Displaying the ESXi version we used for testing: [root@localhost:~] esxcli system version get
Product: VMware ESXi
Version: 6.0.0
Build: Releasebuild-3620759
Update: 2
Patch: 34
Displaying the VAAI support status as reported from DS8000 for thick standard (0x1000) and
ESE volume (0x1100) on our ESXi host: [root@localhost:~] esxcli storage core device vaai status get -d
naa.6005076307ffd7690000000000001000
naa.6005076307ffd7690000000000001000
VAAI Plugin Name:
ATS Status: supported
Clone Status: supported
Zero Status: supported
Delete Status: unsupported
[root@localhost:~] esxcli storage core device vaai status get -d
naa.6005076307ffd7690000000000001100
naa.6005076307ffd7690000000000001100
VAAI Plugin Name:
ATS Status: supported
Clone Status: unsupported
Zero Status: supported
Delete Status: supported i.e. SCSI UNMAP is supported for thinly provisioned volume space reclamation
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1.3 Virtual Machine Cloning
Our source virtual machine “Win2016_DS8k” which we are using for cloning was created with
the default VM disk format of “thick provision lazy zeroed” as shown in Figure 1:
Figure 1: vCenter Server VM Settings for source VM virtual disk type
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Within the vSphere Web Client connected to our vCenter Server we cloned the existing VM
“Win2016_DS8k” with its datastore “DS8k_STD_1000” located on DS8880 thick volume 0x1000
to another datastore “DS8k_ESE_1100” on DS8880 thin volume 0x1100 like shown in Figure 2
and Figure 3.
Figure 2: Using the vSphere Web Client for cloning a VM
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Figure 3: vSphere Web Client selection of the thin target datastore on the DS8880 for cloning the VM
Looking at the disk usage within our Microsoft Windows Server 2016 virtual machine we can
see that the VM has ~11 GB of its 60 GB virtual machine disk (VMDK) allocated as shown in
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The DS8880 thinly-provisioned ESE volume 0x1100 for the cloned VM also shows about 11 GB
allocated (“realcap”) as the DS8880 recognizes the trailing zeroes of the unallocated space from
the 60 GB volume: dscli> showfbvol 1100
Date/Time: 01 August 2017 17:35:14 CEST IBM DSCLI Version: 7.8.20.280 DS: IBM.2107-75GNC81
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1.4 Virtual Machine Deletion
We delete our previously created VM clone “Win2016_DS8k_Clone” again like shown in Figure
5 which logically deletes its associated VM disk files from the datastore and allows us to be able
to demonstrate reclaiming the corresponding DS8880 thinly-provisioned storage space.
Figure 5: Using the vSphere Web Client for virtual machine deletion
1.5 Space Reclamation for IBM System Storage DS8880
From the VMware ESXi host point of view the VM files for the deleted VM
“Win2016_DS8k_Clone” have already logically been deleted from the datastore
“DS8k_ESE_1100”: [root@localhost:~] ls -l /vmfs/volumes/DS8k_ESE_1100
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However the previously used VM storage capacity is still allocated within the thinly provisioned
volume on our DS8880 storage system but can be reclaimed by manually invoking the VAAI thin
provisioning primitive for SCSI UNMAP from our ESXi host on the corresponding datastore
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tierassignerror -
tierassignorder -
tierassigntarget -
%tierassigned 0
etmonpauseremain -
etmonitorreset unknown
GUID 6005076307FFD7690000000000001100
1.6 Summary
Our usage example showed that with the new DS8880 R8.2.3 support for VMware VAAI thin
provisioning space reclamation we were able to reclaim about 92% of the previously allocated
capacity within our thinly-provisioned VMware datastore volumes. The cirumstance that we
weren’t able to reclaim 100% is mainly related to the 16 MiB extent boundary where storage
space can only be reclaimed if it spans across a whole extent.
References
IBM DS8880 Thin Provisioning (REDP-5343) http://www.redbooks.ibm.com/redpapers/pdfs/redp5343.pdf
IBM DS8000 Series Version 8 Release 2.3 Command-Line Interface User’s Guide (SC27-8526-05) http://www-01.ibm.com/support/docview.wss?uid=ssg1S7005236&aid=1
ESXCLI Commands for VAAI operations (2131056) https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2131056
Using the esxcli storage vmfs unmap command to reclaim VMFS deleted blocks on thin-