Proxmox: Low Fsync Performance / SAS2308 / Better use ZFS?

evlute

New Member
Oct 5, 2015
19
0
1
Hallo,

we are having very low FSYNCS/SECOND Values:

CPU BOGOMIPS: 100578.12
REGEX/SECOND: 1277810
HD SIZE: 68.78 GB (/dev/dm-0)
BUFFERED READS: 509.31 MB/sec
AVERAGE SEEK TIME: 0.12 ms
FSYNCS/SECOND: 99.37
DNS EXT: 52.40 ms
DNS INT: 75.71 ms ()

Controller: LSI Logic / Symbios Logic SAS2308
Given: Raid 10: 4x - 1TB Harddisk (storage)
Given: Raid 1 : 2x - Samsung 850 Pro SSD's (512 GB)

After reading a lot i think it is because the LSI Logic only supports write through. My next plan is to try ZFS which needs direct hard disk access. In the Proxmox wiki there is a hint: to use LSI Controller in flashed in IT Mode. Our LSI works in IR Mode. Should still work for ZFS right?

Which ZFS Configuration made sense? Our Server has 64 GB Ram - so it would be okay to reserve 8 GB / TB.

Thanks for your help.

Regards
Evlute
 

macday

Member
Mar 10, 2010
408
0
16
Stuttgart / Germany
Hallo,

we are having very low FSYNCS/SECOND Values:

CPU BOGOMIPS: 100578.12
REGEX/SECOND: 1277810
HD SIZE: 68.78 GB (/dev/dm-0)
BUFFERED READS: 509.31 MB/sec
AVERAGE SEEK TIME: 0.12 ms
FSYNCS/SECOND: 99.37
DNS EXT: 52.40 ms
DNS INT: 75.71 ms ()

Controller: LSI Logic / Symbios Logic SAS2308
Given: Raid 10: 4x - 1TB Harddisk (storage)
Given: Raid 1 : 2x - Samsung 850 Pro SSD's (512 GB)

After reading a lot i think it is because the LSI Logic only supports write through. My next plan is to try ZFS which needs direct hard disk access. In the Proxmox wiki there is a hint: to use LSI Controller in flashed in IT Mode. Our LSI works in IR Mode. Should still work for ZFS right?

Which ZFS Configuration made sense? Our Server has 64 GB Ram - so it would be okay to reserve 8 GB / TB.

Thanks for your help.

Regards
Evlute

Hi ZFS will not help you. You should use a Raid-Controller with writeback-cache and everything is fine with the fsyncs.
 

evlute

New Member
Oct 5, 2015
19
0
1
IMPORTANT: Do not use zfs on top of hardware controller which has it's own cache management. Zfs needs to directly communicate with disks, an HBA adapter is the way to go (or something like LSI controller flashed in 'IT' mode)

I don't think soo macday, because the our requirements seems to be fine for zfs.
 

macday

Member
Mar 10, 2010
408
0
16
Stuttgart / Germany
IMPORTANT: Do not use zfs on top of hardware controller which has it's own cache management. Zfs needs to directly communicate with disks, an HBA adapter is the way to go (or something like LSI controller flashed in 'IT' mode)

I don't think soo macday, because the our requirements seems to be fine for zfs.

believe me...last week i did my 25th proxmox installation in production...and i testet zfs a lot...always gone back to hardware raid or san on lvm
 

evlute

New Member
Oct 5, 2015
19
0
1
okay, which raid controller do you prefer? it should be fast, not to expensive and should give me good overall performance.
 

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