Poor SSD performance in

M

Mark Komarinski

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Apr 27, 2019
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If I do any kind of heavy writes (1GB+) in any of my Linux guests it eventually causes the load to spike and suddenly all the other guests and proxmox itself grinds to a halt.

I'm using ZFS with mirrored 120GB SSDs. I have another ZFS pair of 240GB SSD drives that I migrated a few of the guests to just to see if that changed anything and it didn't seem to. The SSDs are el-cheapo from MicroCenter (think $20 and $40/ea).

I don't see similar behavior when logged into proxmox itself, so I'm guessing either something is misconfigured or something else is going on.
 
Mark Komarinski said:
If I do any kind of heavy writes (1GB+) in any of my Linux guests it eventually causes the load to spike and suddenly all the other guests and proxmox itself grinds to a halt.

I'm using ZFS with mirrored 120GB SSDs. I have another ZFS pair of 240GB SSD drives that I migrated a few of the guests to just to see if that changed anything and it didn't seem to. The SSDs are el-cheapo from MicroCenter (think $20 and $40/ea).

I don't see similar behavior when logged into proxmox itself, so I'm guessing either something is misconfigured or something else is going on.
Click to expand...

As tom said, cheap SSD's will have a small bit fast NAND as a cache layer and then the rest will be cheap NAND, hence you're facing the issue when writing a large file over 1GB you're filling the faster layer and moving into the slow area and getting large I/O wait.
 
sg90 said:
As tom said, cheap SSD's will have a small bit fast NAND as a cache layer and then the rest will be cheap NAND, hence you're facing the issue when writing a large file over 1GB you're filling the faster layer and moving into the slow area and getting large I/O wait.
Click to expand...

Would some DC S3700s be better? I don't need a lot of space (200GB is more than enough).
 
Ok, did a bit of testing and was able to create an LVM-over iSCSI to my FreeNAS box and moved one of my guests over. Sequential writes increased by a factor of 5 and I/O load never crossed 20%. So enterprise SSDs or iSCSI it is.
 
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