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High storage latency on ESXi host
(alien.top)
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this post was submitted on 22 Nov 2023
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15-30ms latency seems reasonable for that hardware (P420 in RAID 10 with 4x4TB 7k SAS HDDs.)
Basically your single SAS disk can do ~150IOPS random, so worst case of 4k random reads you will get ~600KBps.
For the migration if it's sequential (depending on filesystem layout), the performance can be different, up to maximum streaming performance of like 100MBs for large sequential reads.
Then 2x for your RAID config.
That is the thing, my total IOPS are less than 150, with 4 disks in RAID 10 I believe I should get 300IOPS due to mirroring. If you look at the graph, red line is transfer in kbps and blue latency, why is it dropping when disk is highly utilised? I will post htop when I’m back from work.
GID VMNAME NVDISK CMDS/s READS/s WRITES/s MBREAD/s MBWRTN/s LAT/rd LAT/wr12953 dns - 1 0.00 0.00 0.00 0.00 0.00 0.000 0.00016904 fw - 2 5.84 0.00 5.84 0.00 0.02 0.000 18.40820481 vcsa - 13 16.58 0.00 16.58 0.00 0.08 0.000 37.582130847 - 2 0.00 0.00 0.00 0.00 0.00 0.000 0.000626694 deb - 2 12.06 0.00 12.06 0.00 0.46 0.000 6.586as you can see the is no much IOPS per VM, like vcsa VM latency I captured is floating between 20 and 100ms, while deb has similar IOPS but lower latency
I think what you want to do is go into your db vm and run a DD or fio or bonnie++ that is at least 2 x the VM RAM, and see what the steady-state disk performance is.
I don’t have db VM, I think you are referring to deb which is short for Debian.