Imagine I have a storage server, we'll assume mixed workload (random and sequential in equal portions, working dataset always smaller than ARC). Storage controller is the ubiquitous M1015/9240i SAS-6. Currently it has magnetic media in a mirror setup, 2x1TB for the root pool, 2x2TB for the data pool. The root pool is nevertheless only 220GB (it started on smaller disks and wasn't expanded, effectively short stroked). The data pool is over 1TB used space.
If I were to use/add/include 2x256gb SSD, would it be better to simply migrate the root pool onto a mirror of SSDs? Or to use 8gb of each SSD as a ZIL (mirrored) and gstripe the rest and use that as an L2ARC?
I'm aware that L2ARC is not persistent, but gets loaded after boot from slower media. I'm also aware a ZIL mainly affects OSYNC writes. So obviously boot will be faster just migrating the root pool to SSD. The machine stays on for a good period of time, so I assume the L2ARC would eventually fill, but until then, I'd be stuck with low random IOPs and lowish sequential writes (seq. reads are OK at 200-300MB/s already).
I'm aware I'll only get TRIM support as a vdev (I think?)
My question is simply whether there is any reason to use SSDs as L2ARC/ZIL rather than as vdevs assuming the root pool fits and that's where most IO is happening.
If I were to use/add/include 2x256gb SSD, would it be better to simply migrate the root pool onto a mirror of SSDs? Or to use 8gb of each SSD as a ZIL (mirrored) and gstripe the rest and use that as an L2ARC?
I'm aware that L2ARC is not persistent, but gets loaded after boot from slower media. I'm also aware a ZIL mainly affects OSYNC writes. So obviously boot will be faster just migrating the root pool to SSD. The machine stays on for a good period of time, so I assume the L2ARC would eventually fill, but until then, I'd be stuck with low random IOPs and lowish sequential writes (seq. reads are OK at 200-300MB/s already).
I'm aware I'll only get TRIM support as a vdev (I think?)
My question is simply whether there is any reason to use SSDs as L2ARC/ZIL rather than as vdevs assuming the root pool fits and that's where most IO is happening.