Lustre discuss - Sep 2010 - ldiskfs-ext4 interoperability question

Our current Lustre servers run the version 1.8.1.1 with the regular ldiskfs.

We are looking to expand our Lustre file system with new servers/storage and
upgrade to all the lustre servers to 1.8.4 as well at the same time. We
would like to make use of the ldiskfs-ext4 on the new servers to use larger
OSTs.

I just want to confirm the following facts:

1. Is is possible to run different versions of ldiskfs on different OSSs of the
same lustre file system.

2. Can I install the Lustre RPMs meant for the ext4 system on our older servers
that were formatted with the older ldiskfs and expect it to work? Do I
have to do any ext3-ext4 conversion or equivalent to make this work?

TIA
Nirmal

On Thu, Sep 30, 2010 at 02:58:37PM -0500, Nirmal Seenu
wrote:
> 1. Is is possible to run different versions of ldiskfs on different OSSs of
the same lustre file system.
Yes.
> 2. Can I install the Lustre RPMs meant for the ext4 system on our older
servers that were formatted with the older ldiskfs and expect it to work? Do I
> have to do any ext3-ext4 conversion or equivalent to make this work?
The disk layout is compatible, so no conversion is needed.
There is just one bug which can be hit when downgrading from ext4-based
ldiskfs to ext3, see bugzilla ticket 22911 (should be fixed in 1.8.4).

HTH

Cheers,
Johann