[Gluster-users] my own unify - raid5 setup, is it possible?

Raghavendra G raghavendra at gluster.com
Mon Feb 15 07:11:21 UTC 2010

Hi Casper,

On Fri, Feb 12, 2010 at 1:32 PM, Casper Langemeijer <casper at bcx.nl> wrote:

> Hi all,
> I've been toying around with glusterfs 2.0.9 and I'm really liking it. I
> very much enjoy it's simple modular design.
> My current test setup is a unify cluster, using a afr/loadbalanced
> namespace.
> Could I duplicate files to multiple data bricks in the cluster to
> provide a raid5-like setup? I very much want to be able to shutdown a
> single machine in the cluster and still have a fully functional
> filesystem. I'm very happy to write the application that does the
> copying over the data bricks myself.

We recommend using distribute translator instead of unify. But with
distribute (even with unify) data is not striped. Both translators (unify
and distribute) are used to aggregate multiple storage nodes into a single
filesystem. If you want to increase read performance using stripe, you can
use stripe translator.

> Another advantage could be that I can decide on a per-file basis how
> many copies of a file exist in the filesystem. (Two would be a minimum
> for me) The real-world scenario: This would be the data filesystem for a
> webserver cluster setup. You can imagine images used on a homepage are
> requested more frequent than others.

replicate (formerly known as afr) does not  support maintaining different
number of replicas for different files.

> I imagine the order in which I specify the subvolumes in the unify
> volume needs to be different over my clients to make good use of the
> multiple copies over the different bricks.
> What problems can I expect with this setup?
> Have others tried a similar setup?
> Am I missing a GlusterFS feature that would implement what I want, in a
> much easier way?
> Thank you for your time!
> Some other minor remarks:
> * Is there a reason the AFR translator is missing in the wiki on:
> http://gluster.com/community/documentation/index.php/Translators ?

AFR is renamed as replicate.

> * The wiki search does not work for small words (AFR for example) This
> is because MySQL full text search indexes are used, and mysql has a
> minimum char length. Add 'ft_min_word_len=2' to the mysql my.cnf file
> (in the mysqld section) To create indexes of 2 and 3 letter words too.
> This results in larger indexes, but I think it's worth it.
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Raghavendra G

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