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Modifying ESXi hosts MaxHWTransferSize, IOPSValue and ATSMode to achieve best performance & reliability ?

Posted on 2016-10-04
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Last Modified: 2016-10-13
Hi People,

This is another follow Up thread from: https://www.experts-exchange.com/questions/28974117/VMware-VMFS-datastore-LUN-PSP-and-settings-differences-across-different-ESXi-hosts.html

When I produce the report of the Best Practice in VMware ESXi deployment with All Flash Array (SSD), I noticed that there are two items I need to set:

MaxHWTransferSize
The VAAI XCOPY MaxHWTransferSize for this host is incorrect: 4096
This should be set to 16386 (16 MB).

IOPSValue
Some of the VMFS LUNs in the multiple ESXi hosts are displaying IOPSValue as N/A and some of them 1000
This should be set to 1. --> Why the value is changed significantly from 1000 into 1 ?

ATSMode
All of the VMFS LUNs in the entire ESXi hosts are displaying ATSMode as N/A.
This should be set to enabled.

Does any ofthose settings can cause any impact or outage to the Production environment or the VMs ?
I'm thinking to configure it just on one ESXi host and hten moving on to the other ESXi host the next day.

Any help and suggestion would be greatly appreciated.

Thanks.
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10 Comments
 
LVL 124
ID: 41827756
They will  not cause outages, but changing any settings on a Production System, is NOT recommended, and you should test these values first before applying them, and then feel comfortable there is no service impact.

Document the settings before and after.
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Author Comment

by:Senior IT System Engineer
ID: 41827792
Documenting is easy, there is powershell script for that.

But the problem is that I only have one Storage array that is used by the Blade servers in production data center.
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LVL 124
ID: 41827799
it will only affect the VMs on that host you have changed the values on.

those values are low risk.
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LVL 8

Author Comment

by:Senior IT System Engineer
ID: 41827888
Andrew,

So here's what I'll do one ESXi host at the time:

1. Backup ESXi settings using http://slymsoft.com/esxi-conf-backup/
2. Put the ESXi host into maintenance mode (evacuate all VMs).
3. make the necessary changes.
4. reboot
5. exit maintenance mode and rebalance DRS cluster

Would that be possible ?
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LVL 124
ID: 41827977
Yes, you may want to add a TEST, with a single VM, of not much importance...
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Assisted Solution

by:gheist
gheist earned 1000 total points
ID: 41830732
It is best to not change any settings ever.
None of them is documented, and IOPs value is calibrated by ESXi, i.e. modifying has no effect.

You can shorten scsi or nfs or iscsi command queues the way SIOC does (start with 64 and go down if encountering heavy latencies)
1
 
LVL 8

Author Comment

by:Senior IT System Engineer
ID: 41830927
GHeist, my current Storage Array vendor is PureStorage: https://support.purestorage.com/Solutions/Virtualization/VMware/ESXi_Configuration/VMware_vSphere_Best_Practices_Guide_for_the_Pure_Storage_FlashArray

Hence I read that document and found some discrepancies.
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LVL 124

Assisted Solution

by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 1000 total points
ID: 41830943
We always change settings based on vendor requirements, Dell, EMC and NetApp, they have common settings that need to be changed!

and EMC and NetApp have Wizards that do it for you!
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LVL 62

Accepted Solution

by:
gheist earned 1000 total points
ID: 41833065
Most likely pure storage knows better how their disks work.
Easiest way to apply settings in absence of setup tool is vcenter host profiles.

VAAI XCOPY is fast VMDK cloning. It is nice to have, but normally you dont clone-deploy ll the time.
Direct benefit is that origin and clone is deduplicated after cloning if array supports it.

IOPSValue - path failover threshold - only pure storage knows that their array can guarantee 1 IO per second at bad times. You cannot guess this.

All settings are in vmkernel mandating host reboot to apply. Having vmotion there is zero impact in rebooting all hosts one after another.
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LVL 8

Author Closing Comment

by:Senior IT System Engineer
ID: 41842771
Thanks all !
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