Multiple ZFS SLOG?

[Republicus]

I have purchased two nvme disks with PLP that I am using for my ZFS SLOG/ZIL. I have room for several more if it turns out to be beneficial that I do so.

While I have successfully added two log devices, my question is if multiple log devices will stripe or give me the performance of more than one nvme disk?

I wish to, if it is beneficial, to have striped mirrors for my SLOG.

For testing, I have added two log devices without mirroring; in this setup are they striped?

        logs
          nvme-SAMSUNG_MZ1WV480HCGL-000MV_S1Y0NY0HB05785         ONLINE       0     0     0
          nvme-SAMSUNG_MZ1WV480HCGL-000MV_S1Y0NY0HC00083         ONLINE       0     0     0

 

[guletz]

Hi,

Slog is read it only in server crash scenario, so is recommended to use 2 slog devices using a mirror. For normal operation all sync write are go to the slog. Be aware that is also recommend to have proffesional slog devices (aka data center quality ) if you do not want to burn your nvme cells very soon.

Good luck / Bafta

 

[wolfgang]

Hi,

For normal operation all sync write are go to the slog.

only small synced write go to the ZIL.
big synced writes go direct to the vdev.

 

[LnxBil]

I have purchased two nvme disks with PLP that I am using for my ZFS SLOG/ZIL.

and you often only use a few GB at most for SLOG. Having big disks for SLOG is not necessary (with respect to the size). Bigger disks, however have sometimes better IOPS due to bigger internal caches and such, so you have to read the specifications carefully.