Dear all,
we used an older server to build up a Freenas system to be used as ESX datastore over ISCSI.
Some hardware details:
- FreeNAS-11.3
- 2 CPUs (Xeon X5672 @ 3.20GHz)
- 32 GB ECC RAM
- IT Mode SAS Controller (No Hardware RAID)
- 12 Discs 7.2K (3 striped vdevs, each RAIDZ2 with 4 discs)
- Compression lz4, DeDup off, Pool usage < 20% (storage)
- ARC Hit ratio around 80%
- 4x GBit Ports, no LACP, MPIO used, Jumbo packets enabled on ESX + Freenas + Switch
I've used a virtual machine for some tests. The vm is stored on Freenas of course.
When writing 8 GByte with blocksize 1M we measured around 510 MByte/s. I'm satisfied with this value, altough I know this blocksize is more theoretical.
But reading those 8 GByte gives only around 190 MByte/s. "top" and "gstat" seems to be fine. We tested each network link in both directions with iperf3, all of them provided 990 MBit - which is fine.
I do not understand, why reading is much slower than writing. Can anyone explain this?. Because of the high ARC hit ratio, I would assume, that disk usage is quite slow.
Any chance to investigate the problem? I will try increasing RAM, but I would not expect more read performance by the current reported values. I appreciate any other hint to tweak performance.
Thanks in advance,
St
we used an older server to build up a Freenas system to be used as ESX datastore over ISCSI.
Some hardware details:
- FreeNAS-11.3
- 2 CPUs (Xeon X5672 @ 3.20GHz)
- 32 GB ECC RAM
- IT Mode SAS Controller (No Hardware RAID)
- 12 Discs 7.2K (3 striped vdevs, each RAIDZ2 with 4 discs)
- Compression lz4, DeDup off, Pool usage < 20% (storage)
- ARC Hit ratio around 80%
- 4x GBit Ports, no LACP, MPIO used, Jumbo packets enabled on ESX + Freenas + Switch
I've used a virtual machine for some tests. The vm is stored on Freenas of course.
When writing 8 GByte with blocksize 1M we measured around 510 MByte/s. I'm satisfied with this value, altough I know this blocksize is more theoretical.
But reading those 8 GByte gives only around 190 MByte/s. "top" and "gstat" seems to be fine. We tested each network link in both directions with iperf3, all of them provided 990 MBit - which is fine.
I do not understand, why reading is much slower than writing. Can anyone explain this?. Because of the high ARC hit ratio, I would assume, that disk usage is quite slow.
Any chance to investigate the problem? I will try increasing RAM, but I would not expect more read performance by the current reported values. I appreciate any other hint to tweak performance.
Thanks in advance,
St