Re: [PLUG] vmware and i.o

If you have only ESX there is very little monitoring available. If you have vSphere the vCenter

appliance provides a wealth of monitoring and performance statistics.

vCenter provides latency statistics for VM disks, and for the underlying physical LUN's as well

as throughput. Since it is not uncommon with physical disks for one VM to use more than it's

fair share of the disk - your problems may be from a neighbor VM and not your problem so you

really can't debug this from inside the VM.

VMware Enterprise Plus versions use Storage I/O control to throttle back I/O on any runaway VM's automatically

so this doesn't happen, and it makes sure each VM gets it's fair share.

Note: VMware support generally says that 80% of support calls for performance are ultimately tied back to disk

performance issues. You didn't mention if you were using local disk ( RAID level, number of spindles )

or iSCSI. Generally these days the trend is to move towards all-flash storage which eliminates many of

these storage problems as disk latencies often drop from 20-40ms down to 1-2 ms, and everything

works much smoother.

However all of this is the responsibility of your VMware administrator.

If you need specific help you can contact me off-list.

Lee

From: "Rita" <rmorgan466@gmail.com>
To: "Philadelphia Linux User's Group Discussion List" <plug@lists.phillylinux.org>
Sent: Wednesday, February 21, 2018 9:02:51 PM
Subject: [PLUG] vmware and i.o

at our lab we use vmware esx (i think) for virtualization. i feel like we are i/o bound for our processes. The process runtime varies too much but I can't provide if its i/o issue or not. The i.o wait percentage is sometimes at 0 and sometimes at 20%. I understand a lot of times I am using the page/buffers which is cached data.

Sometimes, I feel the underlying disks the VM is using is having problems but being a guest I can't provide that. Is there a way to prove that from a guest point of view?

--
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Lee Marzke, lee@marzke.net http://marzke.net/lee/
IT Consultant, VMware, VCenter, storage, infrastructure, cloud migration options
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