Re: huge filesystems

[Miklos Szeredi]

> The group I work in has been experimenting with GFS and Lustre, and I did
> some NBD/ENBD experimentation on my own, described at
> http://dcs.nac.uci.edu/~strombrg/nbd.html
> 
> My question is, what is the current status of huge filesystems - IE,
> filesystems that exceed 2 terabytes, and hopefully also exceeding 16
> terabytes?
> 
> Am I correct in assuming that the usual linux buffer cache only goes to 16
> terabytes?

The page cache limit is PAGE_CACHE_BITS + BITS_PER_LONG - 1.  On i386
that's 12 + 32 - 1 = 43 bits or 8Tbytes.  On 64 bit architectures the
size of off_t is the only limit.

> Does the FUSE API (or similar) happen to allow surpassing either the 2T or
> 16T limits?

The API certainly doesn't have any limits.  The page cache limit holds
for FUSE too, though with the direct-io mount option the page cache is
not used, so the limit could be removed as well.  I'll fix that.

Thanks,
Miklos
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