freebsd stable - Jun 2016 - HAST, zfs and local mirroring

On Tue, May 31, 2016 at 11:18:32PM +0500, Eugene M. Zheganin wrote:
> Hi.
> 
> I wat to start using HAST, I have two nodes and a pair of disk on each 
> node. So I want to use HASt in an environment where each HAST resource 
> would be mirrored. What is the preferred approach if I want to use ZFS 
> on an end-device to avoid exsessive fscking, and, in the same time, I 
> want to have some redundancy on a block level ? I see two possibility: 
> HAST on a zvol of a mirrored pool, and a ZFS on a hast. But recently I 
> heard that nested zfs (like zfs on zvol) is clamed unsupported. 
> Futhermore, I have zfs on a geli on a zvol, and this solution proved 
> itself to be very affected to livelocking - when disk i/o on a such fs 
> is above some treshold, system is locking, and the only way out is to 
> reset it. Should I chose geom_mirror to provide a device for HAST and 
> the build ZFS on it ?
Only FS support changed data bypass FS layer is Files-11 ODS-2 level,
may be hardware support required.

Can you use ZFS mirror with one vdev local and other vdev by iSCSI?
Every node using separate ZFS pool in this case.

Hi.

On 01.06.16 18:23, Slawa Olhovchenkov wrote:
>
> Only FS support changed data bypass FS layer is Files-11 ODS-2 level,
> may be hardware support required.
>
> Can you use ZFS mirror with one vdev local and other vdev by iSCSI?
> Every node using separate ZFS pool in this case.
If you mean that I should distribute the HAST one-disk device via iSCSI
and then use it as a half of zfs mirrored pool on each node, then I
should ask how the pool will decide which half is more recent - local or
iSCSI, after I will import it and the kernel will found that it's vdevs
differs a lot ? And why should I prefere this overcomplicated scheme
over the geom_mirror, which seems rather simple when comparing. Seems
like I can point HAST to /dev/mirror/whatever device, right ?

Thanks.
Eugene.