Using 2 SSD's to create a SLOG

[Freddie Cash]

On Fri, Jul 11, 2014 at 12:18 PM, javocado <javocado at gmail.com> wrote:

> Thank you for your feedback. We understand that the devices are mirrored
> and tolerant.
> To further my understanding, confirm that I should be able to yank one of
> the SLOG SSD drives and zfs won't care, and I can subsequently replace it
> (issuing what command?) and zfs will then re-mirror it? And if both drives
> are removed then only the sync data would be lost? But if the drives are
> restored, or in the case of a power loss when the server comes back up, the
> sync data on the SSD's will be processed once zfs starts?
>

http://man.freebsd.org/zpool

:)

Read the parts about "attach" and "detach".

"attach" will add a drive to an existing single-drive vdev, thus converting
it to a 2-way mirror vdev.

"attach" can also be used to add a drive to an existing mirror vdev, thus
converting it to a 3-way​ mirror vdev.

"detach" removes a drive from an existing mirror vdev.

So, if you have a 2-way mirror vdev, and one drive is dying, you can attach
a new drive to it (converting it to a 3-way mirror), wait for it to
resilver, then detach the dying drive.  That way, you never lose redundancy
in the mirror vdev.  :)

​--
Freddie Cash
fjwcash at gmail.com