Slow perf: removing zfs intent log and l2arc

[DynFi User]

We have a Proxmox install where everything is up and running and up to date (5.2.5)… but with ridiculously slow performances (write) on the disks. For a dual socket with 256GB of RAM and SAS 10K disks this is really bad…

System has been formated with two SSD (Mirror) for the system on dedicated ZFS pool
…and another ZFS pool (RAIDZ-2) for data / local storage.

On the Storage pool there is an SSD which has been added for the ZIL / ARC log.
This disk has been partitioned in two : one part for the ZIL and another for the ARC logs.

Somehow I am suspecting this setting to be the root cause of our "slow perf problem".
I am not sure if the partition are handled correctly by ZFS which might expect full disk for his Logs.


My question is the following: is it safe to remove a ZIL / L2ARC log on a production system ?
With a command such as:

# zpool remove /dev/sdf1​

Where /dev/sdf1 is the ZFS Intent Log partition.
Normally it is safe, but I've rather ask before taking such action on production system.


Any hint on this will be welcome.

 

[mailinglists]

It is safe, but with a correct command.
I'm on my way out of the office to check exact syntax, but i think your command is missing pool name.
Probably something like zpool remove rpool /dev/logdevicepath
You can see them with zpool status -v.

 

[DynFi User]

Yes - ok

Thanks a lot.

 

[guletz]

Hi,

Can you show more info about your setup, like:
- what kind of test you use for your conclusion
- what kind of ssd's do you use
- hw specification for server
- how is zpool status, arc_summary, zfs list