16TiB ext4
Eric Sandeen
sandeen at redhat.com
Mon Jan 5 18:16:08 UTC 2009
Curtis Doty wrote:
> I'm horsing around with ext4 again. This time on Fedora 10. Is there any
> sane reason why I cannot use the *full* 16TiB volume?
>
> ----8<----
> # vgcreate foo /dev/mapper/mpath*
> Volume group "foo" successfully created
> # lvcreate -L16T -nbar foo
> Logical volume "bar" created
> # mkfs.ext4 -Tlargefile4 /dev/foo/bar
> mke2fs 1.41.3 (12-Oct-2008)
> mkfs.ext4: Size of device /dev/foo/bar too big to be expressed in 32 bits
> using a blocksize of 4096.
> ----8<----
>
> But it appears to *really* allow up to one PE less than the full 16TiB,
> why?
The real limit, IIRC, is (2^32 - 1) blocks, or 4k shy of 16T for 4k blocks.
This is a little unfortunate since "lvcreate -L16T" is so handy, but it
won't mkfs properly. (ext3 should have the same limitation).
We should probably make mkfs just silently lop off one block if it
encounters a boundary condition like this ...
-Eric
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