Question about cache on an SSD with my setup.

[Rob_Z71]

As I'm not familiar with ZFS and still learning. I wanted to ask a question.

I have a pair of WD Red 8TB NAS HDD - 5400 RPM SATA 6 Gb/s 128MB Cache - WD80EFZX2. Got them setup in a mirrored pair. Use case, backups of PC and mobile devices around the house. Obviously with these drives being 5400 rpms they tend to be a bit slow. I have a few 64GB SSD's floating around in a box.

Would there be any value adding one as cache device to the setup to increase speed for backups? If this was a raid of some sort I'm sure there would be value but I'm not so sure with a mirror pair.

 

[danb35]

Highly unlikely that adding an SSD as a cache (L2ARC) device would benefit you--not because your disks are mirrored (a cache device will help a mirror in the same way as it will parity RAID), but because your use case (1) relies much more on writes than reads, and (2) to the extent it is doing reads, it isn't reading the same data over and over.

 

[Rob_Z71]

Yeah figured it might not help much. Well that will keep me from having to open the box back up. Thanks!