[HAST] ZFS, many disks, write order

Tue Sep 22 07:37:14 UTC 2015

One of the great Hast Features is that it Hides Disk Failures from ZFS,
this has been already discussed on this List a few Months ago.

Single ZIL Flash Drive is also not such a great Idea. I whould suggest
to start from scratch with "ZFS Best Practices".

Am 21.09.2015 um 23:10 schrieb Ben RUBSON:
> Hello,
> 
> I plan to use HAST to synchronize a ZFS pool between 2 servers.
> The ZFS pool has 3 RAID-Z2 VDEVs (8+2), + 3 spares.
> +1 mirror for SLOG.
> +1 mirror for L2ARC.
> So a total of 37 disks (4TB each).
> 40Gb/s network bandwidth between the 2 servers.
> 
> Will I have to define each of the 37 disks/resources in hast.conf ?
> Stupid question, but will this setup (with so many resources) work ?
> 
> Will write IOs be ordered on the secondary node in the same order (over all the 37 devices) as they occurred on the primary node ?
> This of course to have the secondary node consistent, even after a power failure of the primary during a high IO load, leading into an import -F <poolname> on the secondary node.
> 
> In HAST, each resource seems to be "independent" from the others.
> In DRBD, as an example, we can put several volumes in a same resource to guarantee write order over all the volumes (disks) of the resource.
> Example :
> 
> resource r0 {
>     volume 0 {
>         device /dev/drbd0;
>         disk /dev/c0v0;
>     }
>     volume 1 {
>         device /dev/drbd1;
>         disk /dev/c0v1;
>     }
> }
> 
> What about HAST then ?
> Of course I would have liked to have my 37 disks as volumes in the same resource, as in the example above.
> 
> Thank you very much for your help !
> 
> Best regards,
> 
> Ben
> 
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