fjmatos
Contributor
Contributor

VSAN 6.7 and Optane Disk: Low Performance

I got a 4 nodes VSAN Cluster VSphere 6.7.0  8169922:

Model:  HP DL380 GEN10

RAM/node:  164 GB

1 disk group per host, w. 1 INTEL OPTANE P4800X 375 GB  for caching  plus 7 SSD 1,8 GB  for capacity.

All the health checks passed.

Using HCIBench the performance is:

100% Read, Random , 4k up to :  280K iops , 1080 MBs throughput , 2,8 ms latency

70/30%  R/W  Random , 4k up to:  180K iops , 700 MBs throughput, 4,4 ms latency

100% Write, Random , 4k up to: 38K iops , 150 MBs  throughput, 20ms latency

The intel optane documentation sais:

Throughput  iops random 4kB R/W:  Up to 550/550k

Throughput  iops random 4kB 70/30 R/W:  Up to 500k

So 4 Optane * 550k gives around 2200 K >> 280 K  iops

Then I must have some problems with my setup.

Someone is using Optane disk and can share his performance results to compare with mine? or give me some advices with

the VSAN configuration and Optane disks?

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mschubi
Enthusiast
Enthusiast

Hello fjmatos,

You can't reach the pure HW metrics due the VSAN SW stack and checksum calculation and .....

Your disk group design isn't so good. A lot of capacity Flash Disks.

Better choose a design with two or three DGs.

If you have 250K front end IOs you have mor than 500k Backend IOs.

Configure HCIBench to produce 10000 IOs and than see R/W latency....

best regards,

Mike

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fjmatos
Contributor
Contributor

Thanks mschubi

I have in mind in the near future, split the discs into two disk groups, adding another  cache disk.

I don´t understand well when you say:

"If you have 250K front end IOs you have mor than 500k Backend IOs."

I think that 250K iops (using 4 optane P4800X 375GB from caching) , is a poor performance, don´t you think?

These optane disk promisse a much better performance than standard SSD disk , but in this case a don´t get great results.

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