SSD for L2ARC and ZIL priority tuning

B

belon_cfy

Hi,

My ZFS storage is using single SSD as L2ARC and ZIL. May I know how can I raise the ZIL write priority to reduce interruption from L2ARC read? I found that the write latency significantly increases when the L2ARC read rate is high.

SSD powered by SandForce SF2000 series is the best choice for such a situation because the write latency won't be affected by read activity; of course the read rate will be slower than the rest of the competitors.

I have already tuned the following parameters for reducing L2ARC write, what else I can do beside this?

Code: 
vfs.zfs.l2arc_noprefetch=0
vfs.zfs.l2arc_feed_min_ms=1000
 
Today we bought another Sandforce based SSD and it performs quite well as a l2arc and zil. The latency is much lower than other non-Sandforce-based SSDs.

I will stick with Sandforce-based SSD for better latency.
 
Try setting
Code: 
vfs.zfs.l2arc_norw=0
in /etc/sysctl.conf

The default prevents writes to L2ARC devices if there ate pending writes. Might not be applicable to shared L2/log devices, but it really helps with large L2 devices and large pools.
 
phoenix said:
Try setting
Code: 
vfs.zfs.l2arc_norw=0
in /etc/sysctl.conf

The default prevents writes to L2ARC devices if there ate pending writes. Might not be applicable to shared L2/log devices, but it really helps with large L2 devices and large pools.
Click to expand...

Thanks for your recommendation, it does help a bit but it still does not completely solve the problem.
 
phoenix said:
Try setting
Code: 
vfs.zfs.l2arc_norw=0
in /etc/sysctl.conf

The default prevents writes to L2ARC devices if there ate pending writes. Might not be applicable to shared L2/log devices, but it really helps with large L2 devices and large pools.
Click to expand...
Does this need to be in /boot/loader.conf instead, so it's set before the pools are mounted?

Kevin Barry
 
You must log in or register to reply here.
Back
Top