[OmniOS-discuss] Slow performance with ZeusRAM?

[Min Kim]

I believe this is an known issue with SAS expanders.

Please see here:

http://serverfault.com/questions/242336/sas-expanders-vs-direct-attached-sas <http://serverfault.com/questions/242336/sas-expanders-vs-direct-attached-sas>

When you are stress-testing the Zeusram by itself, all the IOPs and bandwidth of the expander are allocated to that device alone.  Once you add all the other drives, you lose some of that as you have to share it with the other disks.

Min Kim

> On Oct 22, 2015, at 12:02 PM, Matej Zerovnik <matej at zunaj.si> wrote:
> 
> Hello,
> 
> I'm building a new system and I'm having a bit of a performance problem. Well, its either that or I'm not getting the whole ZIL idea:)
> 
> My system is following:
> - IBM xServer 3550 M4 server (dual CPU with 160GB memory)
> - LSI 9207 HBA (P19 firmware)
> - Supermicro JBOD with SAS expander
> - 4TB SAS3 drives
> - ZeusRAM for ZIL
> - LTS Omnios (all patches applied)
> 
> If I benchmark ZeusRAM on its own with random 4k sync writes, I can get 48k IOPS out of it, no problem there.
> 
> If I create a new raidz2 pool with 10 hard drives, mirrored ZeusRAMs for ZIL and set sync=always, I can only squeeze 14k IOPS out of the system.
> Is that normal or should I be getting 48k IOPS on the 2nd pool as well, since this is the performance ZeusRAM can deliver?
> 
> I'm testing with fio:
> fio --filename=/pool0/test01 --size=5g --rw=randwrite --refill_buffers --norandommap --randrepeat=0 --ioengine=solarisaio --bs=4k --iodepth=16 --numjobs=16 --runtime=60 --group_reporting --name=4ktest
> 
> thanks, Matej_______________________________________________
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