[ZFS] Using SSD with partitions

[Daniel Kalchev]

On Oct 16, 2011, at 17:16 , Luchesar V. ILIEV wrote:

> 6. If, OTOH, you're running a reasonably recent -STABLE (8 or 9), then
> your zpool version is likely 28 (thanks, pjd@), which means ZIL is not
> that scary, but you might still lose some data. Even an unexpected power
> failure might cause trouble, unless the SSD is designed to handle it
> gracefully (this typically involves some sort of capacitor).

Just for the record: even without ZIL, you will most definitely lose data at power outage. In most cases, this will not damage the ZFS filesystem, but data will be lost. There is nothing that can prevent this.

Therefore, with ZFS v28, adding ZIL does not introduce any more risk to your data.

One thing to have in mind is ZIL will help only under certain workloads, sequential write is not one of these. It helps most with database-type loads and sync writes like an NFS server that is written heavily. Freddie have good advice on determining if it will help.

L2ARC on the other hand may help enormously, especially if the spool is big. Workstation-class motherboards until recently were topped at 8GB RAM and ZFS is happy with as much RAM as you can offer. Adding L2ARC may provide more headroom. Benefits of course depend on the workload. Neither L2ARC or ZIL provide magical benefits.

Daniel