Vmware Disk Io question

Daniel333

All,

Having a weird problem. What would you say the normal write rate or write IO would be for a Linux, (centOS vm) sitting there doing nothing?

I have an envionment of 40 Vms using about 1 meg per second. but we have not even installed a app yet. Any idea why it would generate that much traffic?

dave330i

Windows generate steady IO w/out app installed. Not sure about Linux.

Daniel333

So here is the problem I have. I have 2500 VMs and mid-day our SAN is begging for mercy.

Many of these dev envionments are just sitting idle (40 Vms per dev envionment) and generate 1meg of traffic. Interestingly enough it's all WRITE traffic. This traffic generates even when we disable all our app.

Is it normaly for 40 centOS VMs to generate that much write traffic doing nothing?

MentholMoose

Daniel333 wrote: »

Is it normaly for 40 centOS VMs to generate that much write traffic doing nothing?

It depends on what is running in those VMs. If those 40 VMs were "minimal" installs and almost nothing is running, then it's probably not normal. If, however, a full desktop environment is running on every VM, then maybe it is. Log into some of these VMs and find out what is generating that IO.

yum install iotop

And sort by writes (arrow key left or right to highlight DISK WRITE).

blargoe

Is it mbps or MB/s? Is it 1 per vm or 1 per 40 vm's? If it's 1mbps per 40 machines, that really isn't much IO at all, like 25kb/s per VM? That's nothing.

Esxtop can give you a higher lever view of io usage relative to the Esx host, if you wanted to rule out the virtualization layer itself as the problem... But that does not sound like enough IO to cause problems; if it is, then your storage is seriously undersized.

jmritenour

Have you check to see if the VM is swapping to disk? I've seen issues before where Java is installed on Linux VMs that cause it to swap to disk, even if there is plenty of available RAM on the hosts, and no resource contention. The way to get around it was to set a memory reservation equal to the amount of RAM allocated to the VM.