Re: Which version of xfs-progs to use on Debian?

[Brian Foster <bfoster@redhat.com>]

On Mon, Nov 14, 2016 at 01:23:50AM -0600, John Henderson wrote:
> Hi,
> 
> I'm trying to determine the optimal combination of kernel version and
> xfs-progs version to use on a Debian Jessie system (for amd64).
> 
> I've searched this mailing list, and noticed the following exchange:
> 
>   http://www.spinics.net/lists/xfs/msg36165.html
> 
> specifically, Dave's response:
> 
>   "As it is, in future the version of xfsprogs will tell you what
> kernel has the same feature support. i.e. xfsprogs 4.2.0 has exactly
> the same code/feature support as kernel 4.2.0. Similarly for
> xfsprogs/kernel 4.3.0."
> 
> I'm also aware that prior to xfsprogs 4.2.0, userspace versioning did
> not match kernel numbering, as noted:
> 
>   https://git.kernel.org/cgit/fs/xfs/xfsprogs-dev.git/refs/tags
>   https://www.spinics.net/lists/xfs/msg33984.html
> 
> So, as I understand the situation, xfsprogs 3.2.x was associated with
> a lot of different 3.x and 4.y (y<2) kernels.  Further, I want to make
> sure to take advantage of all the (current and future) reliability
> improvements of the new xfs v5 on-disk format, which means (from what
> I follow) that I need at least kernel 3.15 and xfsprogs 3.2.0, as seen
> here:
> 
>   https://www.spinics.net/lists/xfs/msg27961.html
> 
> My main concern focuses on the options currently available in Debian
> (primarily Jessie + backports).  Here's the matchup of what Debian
> ships (jessie, jessie-bpo, and stretch):
> 
>                       linux-kernel     xfs-progs
> Jessie:               3.16.36          3.2.1
> Jessie Backports:     4.7.8            4.3.0
> Stretch:              4.8.5            4.3.0
> 
> So, at first pass, I could just use native jessie's kernel 3.16.36 and
> xfsprogs 3.2.1 (and they seem to match well, as they were released
> together).  However, I actually have to use a more recent kernel
> anyway for some SkyLake support issues.  So, that takes us to at least
> kernel 4.7.8.  I note, though, that jessie-backports is *not*
> packaging xfsprogs 4.7 alongside its kernel (but instead xfsprogs
> 4.3.0); similar issues exist for the 4.8.5 kernel from stretch.
> 

Others might be able to chime in on this, but that strikes me as a
packaging issue. My understanding is that the marriage between the
kernel revision and xfsprogs revision tracking numbers is to help define
dependencies between the two. That said, it might not be a problem for
you if you aren't using anything notable introduced between 4.3 and 4.7.

> Assuming I stick to binary packages distributed through the official
> Debian repos, what's the recommendation of the xfs experts: would I be
> better off (in terms of reliability) with xfsprogs 3.2.1 or xfsprogs
> 4.3.0 used with kernel 4.7.8?  As an alternative, would it be even
> better for me to use xfsprogs 4.7 (via compiling from source, even
> though I'd rather not)?
> 

v4.7 of xfsprogs is probably best, but IMO, you'll probably be fine with
the v4.3 in the simple cases (you haven't mentioned whether you're
planning to use xfsprogs for anything beyond mkfs and possibly repair if
something goes wrong). Just keep in mind that it is out of date with
respect to your kernel in the event that you do run into problems down
the road and may want to update.

> Also, what are current best-practice parameters for 'mkfs.xfs' in
> order to optimize reliability?  Filesystem size is ~10 TB on top of
> LUKS-encrypted Software RAID-1 (using enterprise 512e drives).
> 
> I'd assume, we'd at least want the following:
> 
>   -m crc=1 finobt=1
> 

Usually it is best to go with defaults. Indeed, crc=1,finobt=1 are both
defaults and have been for a while now. See commit 566ebd5a ("mkfs:
default to CRC enabled filesystems") which first appeared in xfsprogs
v3.2.3. I'm not aware of any special/magic options required for raid1 or
encryption.

Brian

> Any pointers to a good write-up on optimizing such creation (and
> later, mount-time) decisions?
> 
> Thanks so much (and for all your work on XFS, too).
> 
> -John
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