[Gluster-users] Block replication with glusterfs for NFS failover

[Runar Ingebrigtsen]

On on. 24. okt. 2012 kl. 08.42 +0200, Brian Candler wrote:
> I don't think it was even accurate. What it probably meant was that NFS
> failover requires inode numbers to be consistent between the two
> filesystems, because inode numbers are used as part of the NFS file handle.
> Block-by-block replication is one way to achieve that.

But it turns out this requirement comes with the use of NFS4, if I'm 
right? NFS3 is stateless, but NFS4 is not.

>>>>     Can I somehow enable block-for-block replication with GlusterFS?
>>>
>>> No. You are reading documentation for something completely different: a pair
>>> of machines synchronised at the block level using DRBD, in a master/slave
>>> configuration (that is: all writes must be made on the master side, and the
>>> block changes are replicated a la RAID1 but over a network).
>>
>> Hm. I don't see how your reply indicates the lack of block-by-block
>> replication in GlusterFS.
>
> GlusterFS replication works at a different layer: each glusterfs brick sits
> on top of a local filesystem, and the operations are at the level of files
> (roughly "open file named X", "seek", "read file", "write file") rather than
> block-level operations.

Hm, does this mean the whole file will be replicated each time it 
changes?
If so, it would seem unfit to store VM images.

--
Best Regards
Runar Ingebrigtsen