Thanks,

I suppose what I'm trying to gain is some clarity on what choice is best
for a given application.  How do I know if it's better for me to use a raid
card or not, to include flash-cache on it or not, to use ZFS or not, when
combined with a small number of SSDs in Replica 3.



On Mon, Apr 9, 2018 at 10:49 AM, Alex Crow <ac...@integrafin.co.uk> wrote:

> On 09/04/18 16:49, Vincent Royer wrote:
>
>
>> Is a flash-backed Raid required for JBOD, and should it be 1gb, 2, or 4gb
>> flash?
>>
>
> RAID and JBOD are completely different things. JBODs are just that,
> bunches of disks, and they don't have any cache above them in hardware. If
> you're going to use ZFS under Gluster, look at the ZFS docs first. Short
> answer is no. If Gluster passes sync writes down to the lower level FS as
> sync, and you decide to use a ZFS SLOG device, usually an SSD, it should
> have power fail protection capacitors.
>
> Do *not* use a RAID controller for ZFS, use a decent HBA instead, so ZFS
> can access the disks directly. Using a RAID controller is not only wasteful
> it's setting yourself up for a world of pain when a ZFS VDEV member device
> fails. Don't do it.
>
>
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