[Gluster-users] GlusterFS on a two-node setup

Mon May 21 12:59:03 UTC 2012

Thanks for confirming this. 

Best,

R.

On Mon, 21 May 2012 08:20:49 +0200,Daniel Müller <mueller at tropenklinik.de> wrote:
> I am running a two node gluster in replication mode. From my experience I
> can tell you in a samba pdc/bdc environment. If one node is down the other
> serves the clients as
> if nothing has happened.

> Greetings
> Daniel

> -----------------------------------------------
> EDV Daniel Müller

> Leitung EDV
> Tropenklinik Paul-Lechler-Krankenhaus
> Paul-Lechler-Str. 24
> 72076 Tübingen

> Tel.: 07071/206-463, Fax: 07071/206-499
> eMail: mueller at tropenklinik.de
> Internet: www.tropenklinik.de
> -----------------------------------------------
> -----Ursprüngliche Nachricht-----
> Von: gluster-users-bounces at gluster.org
> [mailto:gluster-users-bounces at gluster.org] Im Auftrag von John Jolet
> Gesendet: Montag, 21. Mai 2012 02:47
> An: Ramon Diaz-Uriarte
> Cc: <gluster-users at gluster.org>; Brian Candler
> Betreff: Re: [Gluster-users] GlusterFS on a two-node setup

> On May 20, 2012, at 4:55 PM, Ramon Diaz-Uriarte wrote:

> > 
> > 
> > 
> > On Sun, 20 May 2012 20:38:02 +0100,Brian Candler <B.Candler at pobox.com>
> wrote:
> >> On Sun, May 20, 2012 at 01:26:51AM +0200, Ramon Diaz-Uriarte wrote:
> >>> Questions:
> >>> ==========
> >>> 
> >>> 1. Is using GlusterFS an overkill? (I guess the alternative would be 
> >>> to use  NFS from one of the nodes to the other)
> > 
> >> In my opinion, the other main option you should be looking at is DRBD 
> >> (www.drbd.org).  This works at the block level, unlike glusterfs 
> >> which works at the file level.  Using this you can mirror your disk
> remotely.
> > 
> > 
> > Brian, thanks for your reply. 
> > 
> > 
> > I might have to look at DRBD more carefully, but I do not think it 
> > fits my
> > needs: I need both nodes to be working (and thus doing I/O) at the 
> > same time. These are basically number crunching nodes and data needs 
> > to be accessible from both nodes (e.g., some jobs will use MPI over 
> > the CPUs/cores of both nodes ---assuming both nodes are up, of course ;-).
> > 
> > 
> > 
> > 
> >> If you are doing virtualisation then look at Ganeti: this is an 
> >> environment which combines LVM plus DRBD and allows you to run VMs on 
> >> either node and live-migrate them from one to the other.
> >> http://docs.ganeti.org/ganeti/current/html/
> > 
> > I am not doing virtualisation. I should have said that explicitly. 
> > 
> > 
> >> If a node fails, you just restart the VMs on the other node and away you
> go.
> > 
> >>> 2. I plan on using a dedicated partition from each node as a brick. 
> >>> Should  I use replicated or distributed volumes?
> > 
> >> A distributed volume will only increase the size of storage available
> (e.g. 
> >> combining two 600GB drives into one 1.2GB volume - as long as no 
> >> single file is too large).  If this is all you need, you'd probably 
> >> be better off buying bigger disks in the first place.
> > 
> >> A replicated volume allows you to have a copy of every file on both 
> >> nodes simultaneously, kept in sync in real time, and gives you 
> >> resilience against one of the nodes failing.
> > 
> > 
> > But from the docs and the mailing list I get the impression that 
> > replication has severe performance penalties when writing and some 
> > penalties when reading. And with a two-node setup, it is unclear to me 
> > that, even with replication, if one node fails, gluster will continue 
> > to work (i.e., the other node will continue to work). I've not been 
> > able to find what is the recommended procedure to continue working, 
> > with replicated volumes, when one of the two nodes fails. So that is 
> > why I am wondering what would replication really give me in this case.
> > 
> > 
> replicated volumes have a performance penalty on the client.  for instance,
> i have a replicated volume, with one replica on each of two nodes.  I'm
> front ending this with an ubuntu box running samba for cifs sharing.  if my
> windows client sends 100MB to the cifs server, the cifs server will send
> 100MB to each node in the replica set.  As for what you have to do to
> continue working if a node went down, i have tested this.  Not on purpose,
> but one of my nodes was accidentally downed.  my client saw no difference.
> however, running 3.2.x, in order to get the client to use the downed node
> after it was brought back up, i had to remount the share on the cifs server.
> this is supposedly fixed in 3.3.

> It's important to note that self-healing will create files created while the
> node was offline, but does not DELETE files deleted while the node was
> offline.  not sure what the official line is there, but my use is archival,
> so it doesn't matter enough to me to run down (if they'd delete files, i
> wouldn't need gluster..)

> > Best,
> > 
> > R.
> > 
> > 
> > 
> > 
> >> Regards,
> > 
> >> Brian.
> > --
> > Ramon Diaz-Uriarte
> > Department of Biochemistry, Lab B-25
> > Facultad de Medicina
> > Universidad Autónoma de Madrid
> > Arzobispo Morcillo, 4
> > 28029 Madrid
> > Spain
> > 
> > Phone: +34-91-497-2412
> > 
> > Email: rdiaz02 at gmail.com
> >       ramon.diaz at iib.uam.es
> > 
> > http://ligarto.org/rdiaz
> > 
> > _______________________________________________
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> > Gluster-users at gluster.org
> > http://gluster.org/cgi-bin/mailman/listinfo/gluster-users

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-- 
Ramon Diaz-Uriarte
Department of Biochemistry, Lab B-25
Facultad de Medicina 
Universidad Autónoma de Madrid 
Arzobispo Morcillo, 4
28029 Madrid
Spain

Phone: +34-91-497-2412

Email: rdiaz02 at gmail.com
       ramon.diaz at iib.uam.es

http://ligarto.org/rdiaz