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October 7th, 2021 07:00
Performance IO Measuring
Hi,
we have two sc5020 Compellent Storage with live Volumes. I would lern more about IO Usage Graphs in Dell Storage Manager. How and where the Storage Manager measure the IOs at level Server and level Volumes? Whats is the difference for this measurement? What wolud be measured in the Charting tab in the Storage Manager. I think about the latency graph. If i see a graph with high latency about 100ms but low IO and not much data transfer (about 100MB/sec) how it can be? I didnot understand how storage manager measure the latency. it can only be the latency at the storage himself. ESX has his own latency graphs. What mean the latency on the storage at about 100ms in peak.
I hope you understand me und clarify my questions.
Thanks very much.
Regards
Robert
Origin3k
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2.3K Posts
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October 7th, 2021 09:00
If you see 100ms of latency than something is broken or going completely wrong. I raise my eye brown when there is >10ms.
"... 100ms but low IO and not much data transfer (about 100MB/sec) how it can be...."
When there is something using a very large blocksize.
To verify what youre seeing in DSM compare it with esxtop 'd'.
As an example. A 10 Host stretched VMware Cluster with LiveVolumes performing right now 1000MB/s with 50K IOPS and the Controller with 5ms read and around 1ms write latency on controller level.
Regards,
Joerg
Robudus
6 Posts
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October 8th, 2021 06:00
Hi, we have about 400 VMs, and about 250 Citrix VDI/VDAs and the latency is about 27ms in peak on the Controller. I did not understand the latency difference in different measure points. The PackageSize is about 45-50KB and IO about 20K.
I can measure on different places, on Volume, on Server, on controller but how the storage System measure the latency and why are the graphs difficult? The same for IO.
Regards
Robert
Robudus
6 Posts
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October 18th, 2021 23:00
It was RDMs from our Windows Clusters. With the Flag
Perennially Reserved Flag for WSFC all Latency go away.
Thanks.
regards ROBudus