i suspect that an rsync with the proper argument will be fine before starting glusterd on the recovered node?. On May 21, 2012, at 7:58 AM, Ramon Diaz-Uriarte wrote: > > > > On Mon, 21 May 2012 00:46:33 +0000,John Jolet <jjolet at drillinginfo.com> wrote: > >> 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. > > OK, great. Thanks for the info. It is clear, then, that several of you > report that this will work just fine. > > >> 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..) > > > That is good to know, but is not something I'd want. Is there any way to > get files to be deleted? Maybe rsync'ing or similar before self-healing > starts? Or will that lead to chaos? > > > > Best, > > R. > > >>> Best, >>> >>> R. >>> >>> >>> >>> >>>> Regards, >>> >>>> Brian. >>> -- >>> Ramon Diaz-Uriarte >>> Department of Biochemistry, Lab B-25 >>> Facultad de Medicina >>> Universidad Aut?noma 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 >>> >>> _______________________________________________ >>> Gluster-users mailing list >>> Gluster-users at gluster.org >>> http://gluster.org/cgi-bin/mailman/listinfo/gluster-users > > -- > Ramon Diaz-Uriarte > Department of Biochemistry, Lab B-25 > Facultad de Medicina > Universidad Aut?noma 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 >
