[Linux-cluster] Re: GFS on md on shared disks?

[Ed L Cashin]

Erling Nygaard <nygaard at redhat.com> writes:

> No, this will not work at all.
>
> All GFS locking is done on a filesystem level. In order to make this work 
> you need locking on the blocksystem level .

I guess I'm looking for a concrete reason why it won't work.  I've
been assuming it won't work, but I can't think of a concrete reason.

You need to lock a resource group to allocate blocks for a file, and
you need to lock the file in order to modify its blocks, so it's not
entirely clear to me why you need block-level locking when md is
involved.

The only concrete problem I can think of is that the md has a
superblock, and no node would know that other nodes are using the same
md superblock.

-- 
  Ed L Cashin <ecashin at coraid.com>