[Linux-cluster] 32bits vs 64bits (was: GFS limits: fs size, etc.)

Ken Preslan kpreslan at redhat.com
Mon Sep 13 16:24:32 UTC 2004

On Mon, Sep 13, 2004 at 06:15:08PM +0200, Axel Thimm wrote:
> On Fri, Sep 10, 2004 at 01:05:03PM -0500, Ken Preslan wrote:
> > For Linux 2.6 on a 32-bit platform, the max filesystem size is 16TB if
> > you trust the sign bit, 8TB if you don't.  This limit comes from the
> > 32-bit page index in the "struct page": 2^32 * 4096 bytes/page = 16TB.
> > 
> > For Linux 2.6 on a 64-bit platform, the max filesystem size is *big*.
> > Something around 2^64 bytes.
> That means that you need to have a cluster of equal-bit-arch members?
> One can certainly not add a 32-bit cluster member to a 64-bit > 16TB
> crafted cluster. What about smaller sized filesystems? Would 32bits
> and 64bits work nicely together, or are there more barriers?

You can happily mix 32-bit and 64-bit machines.  As you said, 32-bit
machines shouldn't access bigger filesystems.  But, you can have a mixed
cluster with the 32-bit machines mounting only smaller the filesystems
and the 64-bit machines mounting anything they want.

Ken Preslan <kpreslan at redhat.com>

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