[Gllug] Maximum size of NFS filesystem under 2.6 kernel

[Daniel P. Berrange]

On Mon, Nov 28, 2005 at 12:44:56PM -0000, Huw Lynes wrote:
> On Sat, 2005-11-26 at 01:31 +0000, Bruce Richardson wrote:
> > What's the maximum size of filesystem that can be exported via NFS under
> > a 2.6 kernel (assuming 2.6 kernel on both server and client)?
> > 
> 
> recently on the XFS list someone was setting up a 300TB filesystem on
> top of LVM exported via NFS. Apparently it's not a problem.

Success or failure with such large filesystems, is very dependant on 
kernel version, disk controller & hard drive. In particular the latter
two have to support the 64-bit SCSI addressing protocol extensions.
And within the kernel there are many layers which can screw things 
up in ways which you won't discover until you find your data is *gone*.
ie, reads will work, writes will work, but somewhere in the stack a
counter will wrap & data ends up in the wrong place. Finally, the MSDOS
partition table format cannot be reliably used for partitions > 2TB.

In RHEL-4 there was alot of testing to get everything working reliably
beyond the 2 TB boundary. Steven Tweedie put together a handy tool
for verifying the correct operation of I/O data paths with large
partitions, which could be handy for anyone contemplating it:

  http://people.redhat.com/sct/src/verify-data/

Regards,
Dan.
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