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I have a VMWare VM I have to use for certain tasks at work. For some reason while the VM is running or suspended something is doing massive (in terms of operations, not Bytes/s) I/O on its .vmem file, making the system on that disk very sluggish.
Resource Monitor basically shows the culprit of the performance problems:
And the top spot in Disk Activity is always taken by the System process accessing said file.
Anyone knows what's going on here?
Joey
Posted 2012-10-30T08:49:22.220
Reputation: 36 381
1Bit of background here on the suspended aspect. When you suspend a VM, it's RAM is written to the VMEM file. Watch resource monitor and you'll see a big block go from green (in use) to orange (modified) when you suspend the VM. Windows then flushes the modified blocks to the VMEM file. This flushing really hammers a SATA-3 drive causing a very unresponsive system. Second the modified memory hits zero, performance returns – munrobasher – 2015-03-19T00:40:49.467
The VMEM activity seems to have got a lot worse on WS11 on Windows 8.1 - I can have just one 3GB VM running on a 16GB host PC and periodically some processes on the host lock up - always VMware workstation itself and sometimes anything else trying to access the same disk where the VMEM file is stored. Interestingly, like the original poster here, bytes/second write is usually relatively low but there are a lot of operations. So the queue length hits the roof but the throughput is nowhere near the raw speed of SATA-3 drives (let's say 80MB/s) – munrobasher – 2015-03-19T00:43:56.133
delayed writes? – Sathyajith Bhat – 2012-10-30T08:50:54.467
Half an hour after the VM was suspended? In packets of roughly 1 MiB/s? – Joey – 2012-10-30T09:22:02.810
just guessing, maybe VMWare's scheduling writes when idle or the like. Curious to know the real reason too – Sathyajith Bhat – 2012-10-30T09:37:03.183
I just tried whether it's the same after a restart, but got a Bluescreen when resuming the VM ... trying again now ;-) – Joey – 2012-10-30T09:46:26.487