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mattwaddy
Contributor
Contributor

VMs Slow Response - Query around %VMWait ESX Stats

I'm looking into an issue within our Citrix environment which has been pointing to CPU oversubscription causing issues. As a result a couple of the VMs have been moved to a new host which is not contended at all. I am however seeing something in ESXTOP which I'm not sure about and wondered if anyone could advise?

Since the move stats for %CSTP and %RDY are pretty much non existant which looks good. However I do see that %VMWait seems to be high which from reading can be a symptom of blocking due to IO waits etc.

For reference all the VMs in question run 6 vCPUs with 32GB mem. The %VMWait always hovers around 6-10% and spikes to %16 on occasion. Now I'm struggling to work out if this is due to IO is there any specific stats that can confirm it or anything else I should be looking at?

%USED    %RUN    %SYS   %WAIT %VMWAIT    %RDY   %IDLE  %OVRLP   %CSTP  %MLMTD  %SWPWT

68.52   67.99    2.06  517.40    3.49   11.98  115.89    2.22    0.03    0.00    0.00

369.47  371.17    3.41  615.95    9.25    8.26  209.22    5.69    0.24    0.00    0.00

77.35   70.19    9.02  524.47    0.98    2.69  125.68    2.11    0.02    0.00    0.00

292.72  292.31    1.70  703.21    9.58    0.12  296.00    1.07    0.00    0.00    0.00

308.00  305.71    3.33  689.81    7.02    0.11  285.45    1.19    0.00    0.00    0.00

Latency for reads is sub 10ms and writes 1-2ms

If anyone can give me some further pointers that would be appreciated.

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homerzzz
Hot Shot
Hot Shot

Are the VMs swapping at all? I ask this not knowing what the HW config is.

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tomtom901
Commander
Commander

VMWAIT is mostly an indicator of a host under I/O pressure. Are there VM's swapping? In esxtop, press the m key, followed by the v key (view VM only). Then check stuff like SWCUR and so on.

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