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VMware datastores design with XtremIO
Hi ,
We have installed 4 brick XIO recently. With sub 1ms latency and high IOP limits do I need to re-disgn my Vmware storage?
Here are a couple of design questions I keep battling over:
1. Are there downside to creating really large datastore for and putting many vms on it? I am thinking of creating 4TB datastores in a cluster for most of the vms.
2. On the flip side would it be feasible create one datastore per vm so you can use snapshots and get rid of your backup licenses for vmware? We only keep vmware image level backups here for 2 weeks.
3. For SQL severs do you really need separate disks for logs and DB anymore?
4. Anyone sharing ESXi hosts among Vmax and XtremIO? What vmware host configuration settings do you use the one for XIO or Vmax?
1. Yes. Here are a few things to consider.
· SCSI lock attention on datastore. This happens during VM creation/deletion/snapshot type of metadata operations
· VM Kernel admittance policy w/ shared datastore. This is controlled by the configuration parameter Disk.SchedNumReqOutstanding, which is default to 32. Disk.SchedNumReqOutstanding will take precedent over queue depth setting if the datastore is shared by multiple VMs.
2. It is always a good idea to separate VM OS/binary backup from SQL DB backups. SQL DB VMDKs should be marked as independent, i.e., not participate in VM snapshot unless you have a tiny database. By the way, you can get rid of the VMware snapshot licensing by using our free VSI plugin and/or AppSync, see a blog post on this topic at
https://itzikr.wordpress.com/2015/07/17/virtual-storage-integrator-6-6-is-almost-here/
3. That’s not necessary anymore w/ XtremIO. See more discussions on SQL on XtremIO best practices paper http://www.emc.com/collateral/white-paper/h14583-wp-best-practice-sql-server-xtremio.pdf
4. If you are using multiple storage arrays with the same ESX server, you should be using the least restrictive settings between the two options. For example, if XtremIO recommends the disk queue depth settings to be set at a very high value compared to the recommended number for VMAX - you should follow the VMAX recommended number for that host. Otherwise you will get very good performance from the XtremIO LUNs, but you will end up hammering the VMAX with a lot of IOs.
dynamox
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Posted November 18th, 2015 10:00
2. Datastore per VM - aren't there limits of how many devices can be presented to an ESX host ?