[CentOS] 32-bit kernel+XFS+16.xTB filesystem = potential disaster (was:Re: ZFS @ centOS)

[Brandon Ooi]

On Tue, Apr 5, 2011 at 10:21 AM, Lamar Owen <lowen at pari.edu> wrote:

>
> You really, really, really don't want to do this.  Not on 32-bit.  When you
> roll one byte over 16TB you will lose access to your filesystem, silently,
> and it will not remount on a 32-bit kernel.  XFS works best on a 64-bit
> kernel for a number of reasons; the one you're likely to hit first is the
> 16TB hard limit for *occupied* file space; you can mkfs an XFS filesystem on
> a 17TB or even larger partition or volume, but the moment the occupied data
> rolls over the 16TB boundary you will be in disaster recovery mode, and a
> 64-bit kernel will be required for rescue.
>
> The reason I know this?  I had it happen.  On a CentOS 32-bit backup server
> with a 17TB LVM logical volume on EMC storage.  Worked great, until it
> rolled 16TB.  Then it quit working.  Altogether.  /var/log/messages told me
> that the filesystem was too large to be mounted.  Had to re-image the VM as
> a 64-bit CentOS, and then re-attached the RDM's to the LUNs holding the PV's
> for the LV, and it mounted instantly, and we kept on trucking.
>
> There's a reason upstream doesn't do XFS on 32-bit.
>

Afaik 32-bit binaries do run on the 64-bit build and compat libraries exist
for most everything. You should evaluate if you really *really* need
32-bit.
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