Hello folks,
I've used DRBD over ZFS for many years and my experience has been very
possitive. My primary use case has been virtual machine backing storage for
Xen hypervisors, with dom0 running ZFS and DRBD. The realtime nature of DRBD
replication allows for VM migrations, etc, and ZFS makes remote incremental
backups awesome. Overall, it is a combination that is hard to beat.
* Key things to keep in mind:
. The performance of DRBD on ZFS is not the best in the world, but the
benefits of a properly configured and used setup far outweigh the performance
costs.
. If you are not limited buy storage size (typical when using rotating
disks), I would absolutely recommend mirror vdevs with ashift=12 for best
results in most circumstances.
. If space is a limiting factor (typical with SSD/NVME), I use raidz, but
careful considerations have to be made, so you don't end up wasting tuns of
space, because of ashift/blocksize/striping issues.
. Compression works great under the DRBD devices, but volblocksize/ashift
details are extremely important to get the most out of it.
. I would not create additional ZFS file systems on top of the DRBD devices
for compression or any other intensive feature, just not worth it, you want
that as close to the physical storage as possible.
I do run a few ZFS file systems on virtual machines that are backed by DRBD
devices on top of ZFS, but I am after other ZFS features in those cases. The
VMs running ZFS have compression=off, no vdev redundancy, optimized
volblocksize for the situation/workload in question, etc. My typical goto
filesystem for VMs is XFS, because it is lean-and-mean and has the kind of
features that everyone should want in a general purpose FS.
If you have specific questions, let me know.
David
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David Bruzos (Systems Administrator)
Jacksonville Port Authority
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Jacksonville, FL 32206
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On Fri, Aug 20, 2021 at 11:32:31AM +0000, Eric Robinson wrote:
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> My main motivation is the desire for a compressed filesystem. I have
> experimented with using VDO for that purpose and it works, but the setup is
> complex and I donโt know if I trust it to work well when VDO is in a stack of
> Pacemaker cluster resources. If there a better way of getting compression to
> work above DRBD?
>
> -Eric
>
>
> From: ra...@isoc.org.il <ra...@isoc.org.il>
> Sent: Thursday, August 19, 2021 4:43 PM
> To: Eric Robinson <eric.robin...@psmnv.com>
> Cc: drbd-user@lists.linbit.com
> Subject: Re: [DRBD-user] DRBD + ZFS
>
> Not sure ZFS is the right choice as an underline for a resource,
> it is powerful but also complex (as a code base), which will probably will
> make it slow.
>
> unless you are going to expose the ZVOL or the dataset directly to be
> consumed,
> stacking ZFS over DRBD over ZFS, seems to me as a bad idea.
>
>
>
> Rabin
>
>
> On Wed, 18 Aug 2021 at 09:37, Eric Robinson
> <eric.robin...@psmnv.com<mailto:eric.robin...@psmnv.com>> wrote:
> Iโm considering deploying DRBD between ZFS layers. The lowest layer RAIDZ
> will serve as the DRBD backing device. Then I would build another ZFS
> filesystem on top to benefit from compression. Any thoughs, experiences,
> opinions, positive or negative?
>
> --Eric
>
>
>
>
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