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Date: Mon, 04 Jul 2016 14:56:03 +0200
From: Miroslav Lachman <000.fbsd@quip.cz>
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To: Julien Cigar <julien@perdition.city>,
 Ben RUBSON <ben.rubson@gmail.com>
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Subject: Re: HAST + ZFS + NFS + CARP
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Julien Cigar wrote on 07/04/2016 14:25:

> another option I had in mind is to export ZVOL through iSCSI:
> - on serverA: $> zpool create storage mirror /dev/ada1 /dev/ada2
> - on serverB: $> zpool create storage mirror /dev/ada1 /dev/ada2
>
> create a 50G dedicated redundant storage for serverC:
> - on serverA: $> zfs create -V 50G storage/serverc
> - on serverB: $> zfs create -V 50G storage/serverc
>
> iSCSI export /dev/zvol/storage/serverc from serverA and serverB and
> create a ZFS dataset on serverC:
> - on serverC: $> zpool create storage mirror /dev/ivol1 /dev/ivol2
>
> (where ivol1 is the volume from serverA and ivol2 the volume from
> serverB)
>
> create, for example, a dataset for the dovecot service
> - on serverC: $> zfs create -o compress=lz4 storage/dovecot

I think it will be painfully slow. ZFS on top of ZFS throught iSCSI... 
too much layering, too much delays.

Miroslav Lachman