[zfs-discuss] recommendations for a 50 TB zpool?

Gordan Bobic gordan.bobic at gmail.com
Sat Nov 3 20:13:12 EDT 2018

IMO, disks much over 4TB are bad news. I suggest you stick with 4TB disks.
Avoid shingled or helium filled disks, or those under 7200rpm. Consult last
few years worth of Backblaze statistics when choosing the disk brand and
model to get.

I concur with you that RAIDZ2 is a reasonable choice for reliability, but
bear in mind that while this will be a reasonable choice for sequential
workloads, performance will be very poor for random read workloads (with
7200 rpm disks, you will get 120 IOPS per vdev).

8-12 disks (or 16-24 with 4TB disks) is IMO too big for a single vdev. It
will affect both performance and reliability. 4x(4+2) would probably be
better if you can afford it. If not, I guess 2x(8+2) configuration wouldn't
be too bad with 4TB drives. Note that random write I/O performance will be
120 IOPS per vdev (480 in first case, 240 in the other). It will be better
for reads at approximately 720 and 300 respectively. Do some testing and
maths to see whether that will suffice for your workload.

On Sat, 3 Nov 2018, 23:34 Ulli Horlacher via zfs-discuss <
zfs-discuss at list.zfsonlinux.org wrote:

> I have to set up a new F*EX (*) server with about 50 TB.
> I will get 8 8-12 TB SAS or SATA disks.
> The throughput will be about 1 TB/d (accumulated read+write).
> Reliabilty is more important than performance.
> Rebuilding of a defect and replaced 12 TB disk will take many hours and in
> this time a second disk failure will be catastrophic.
> Therefore I thought of using RAIDZ2.
> So far I have used ZFS only with 2-disk-RAID1.
> Any recommendations for my use case?
> The OS will be CentOS (decision set by management, no discussion possible).
> (*) https://fex.rus.uni-stuttgart.de/
>     https://fex.rus.uni-stuttgart.de/features.html
> --
> Ullrich Horlacher              Server und Virtualisierung
> Rechenzentrum TIK
> Universitaet Stuttgart         E-Mail: horlacher at tik.uni-stuttgart.de
> Allmandring 30a                Tel:    ++49-711-68565868
> 70569 Stuttgart (Germany)      WWW:    http://www.tik.uni-stuttgart.de/
> REF:<20181103233358.GA15759 at rus.uni-stuttgart.de>
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