ZFS Warning Since Upgrade to 10.0

[Steven Hartland]

----- Original Message ----- 
From: "Tim Gustafson" <tjg at ucsc.edu>
To: <freebsd-fs at freebsd.org>
Sent: Monday, September 22, 2014 5:14 PM
Subject: ZFS Warning Since Upgrade to 10.0


>I recently upgraded a ZFS file server from 9.2 to 10.0 and then
> started getting this warning when I run zpool status:
> 
> status: One or more devices are configured to use a non-native block
> size. Expect reduced performance.
> action: Replace affected devices with devices that support the
> configured block size, or migrate data to a properly configured pool.
> 
> I Googled around a bit, and understand the warning, but I have a
> problem: that zpool is 135TB and I don't have 135TB of disks laying
> around, nor the controllers necessary to support an additional 135TB
> of disks, to migrate this zpool to a properly configured one, nor
> could I easily have the server off-line for the requisite time that
> would be required to transfer 100+ TB of data from one set of hard
> drives to another.
> 
> So my questions are:
> 
> How much will this sub-optimal configuration affect performance?

That depends on your disks, as native 4k drivers when you send a 512
write it has to perform a COW operation.

The only real way to tell is to compare the two in a test with your
setup.

> Does the upgrade to 10.0 represent a reduction in performance, or was
> the reduction in performance always there and just not reported?  This
> server is used to store genome data, so performance is pretty
> important, but the users were happy with the performance when it was a
> 9.2 server.

The issue was always there, its just ZFS now reports the issue.

> If I convince the users to go through an upgrade process to fix this
> issue, how much of a boost in performance can they expect to see?  If
> it's a 2% boost, I don't think I can get them to invest in the
> upgrade, but it it's a 100% boost, I'm pretty sure I can.

Impossible to say, you could test on a smaller install if you want
to be sure.

    Regards
    Steve