default file system, was: Comparison to Workstation Technical Specification

[Chris Murphy]

On Feb 26, 2014, at 9:41 PM, Kevin Fenzi <kevin at scrye.com> wrote:

> On Wed, 26 Feb 2014 21:13:58 -0700
> Chris Murphy <lists at colorremedies.com> wrote:
> 
>> 
>> On Feb 26, 2014, at 1:54 PM, Kevin Fenzi <kevin at scrye.com> wrote:
>> 
>>> Another aspect of xfs we may want to investigate and get feedback
>>> from filesystem folks is how well xfs works on 32bit these days. 
>>> 
>>> RHEL7 doesn't have a 32bit version in their beta, so they only need
>>> to support 64bit xfs. Does the fact that we expect to have 32bit
>>> workstation and/or server weigh into this decision any?
>> 
>> I think the only limit is 16TB max file system, so off hand I'd say
>> no. But this also applies to ext4.
>> 
>> I just tested with 3.13.4-200.fc20.i686+PAE.
>> 
>> XFS (sdc): file system too large to be mounted on this system.
>> EXT4-fs (sdc): filesystem too large to mount safely on this system.
>> 
>> The same 32-bit kernel mounts a 20TB Btrfs volume with no complaints,
>> so I don't know its limit.
>> 
>> http://paste.fedoraproject.org/80784/93470280/
>> 
>> XFS mounts with inode64 by default, same as x86_64. So that's good.
> 
> I wasn't referring to filesystem size limits... there was some issue
> with Xfs and linux kernel stacks on 32bit linux causing crashes and
> data loss.

Yes I know. Even 32-bit mkfs will make a much bigger file system, it just won't mount it. I'm only finding some things 2+ years old suggesting it was once possible to mount XFS bigger than 16TB on 32bit OS, but after filling it (mounted rw) to just beyond 16TB then the kernel would panic and that was the end of accessing the volume from a 32bit kernel.

inode64 is important even for 32bit because otherwise all the inodes end up in the first 1TB and the whole file system is wonky and slow if it's sufficiently large.

> I don't know if this has been fixed, no longer applies or just has been
> ignored by only using it on 64bit machines, but before we go making it
> a default and shipping it on 32bit, we should ask around about it. ;)

Sure, I agree. I will ask on the XFS list and also include armv7hl in the inquiry even though I'm not certain they are interested in XFS (?).

Chris Murphy