2**31-1 blocks question

Eric Sandeen sandeen at redhat.com
Tue May 11 13:51:42 UTC 2010

Mag Gam wrote:
> We need to create very large filesystems. We prefer to have a
> filesystem which is 12TB but it seems ext3 does not suppor that.

Most recent ext3 kernelspace and userspace should technically
make it to 16T.

> Everytime, we do mkfs.ext3 on a 12TB LV we get
> mke2fs: Filesystem too large.  No more than 2**31-1 blocks
>          (8TB using a blocksize of 4K) are currently supported.

Newer e2fsprogs should have lifted this restriction.
Note however that a filesystem this large will probably be almost
impossible - at least very slow - to run fsck on.

> We can override that by doing,
> mkfs.ext3 -b 8192
> But what is the downside for doing this? By using a larger blocksize
> what are the consequences?

The downside is you probably can't mount it, because it's 
block size > page size on most architectures (like x86 and x86_64)


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