Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
/ 2004-07-02 20:15:55 +0200 \ Stefan Andersson: > Hello, > > I'm in the process of building a fault tolerant system, and > have looked at drbd and the recent GFS release by redhat. > > What I ideally would like to have is > > 1. one filesystem shared among a number of nodes, with write > access at all nodes. "shared storage" (shared scsi) would > introduce a single point of failure, so I'm thinking more > in the lines of storage replication, i.e. what drbd is doing. > > 2. arbitrary node(s) may fail, and be resynchronized after repair > > 3. good performance > > Now, as I understand drbd works only in a primary/secondary > configuration, where all writes at paul/primary is replicated to > silas/secondary, and their roles can switch with heartbeat software. > > The two node configuration may be sufficient for our needs, but it > would be a nice bonus to be able to mount the file system from three, > four nodes. Will perhaps GNBD (gfs network block device) solve this > instead of using drbd? (but, as far as I can tell, it will only have > one primary and is mainly for load balancing and not fault tolerance) > > Would it be possible to use GFS on top of DRBD to get write support at > both nodes? I.e. does drbd replicate writes at silas to paul? not yet. but GFS support is on our list. somewhen... depending on time, human resources, and cash-flow :) > Another acceptable solution would be to use for example ext3 on the drbd > replicated block device. Now, I've understood that it is not adviced to mount > the filesystems at the secondary node because the FS will change under > its feed because it is not aware of another host writing. My question > is, would it be possible to mount the filesystem readonly at silas? No. But you could use lvm snapshots, and do your readonly access on the static snapshot, for backup or anything else which is happy with slightly outdated, but consistent, data. have a look at the drbd and lvm and snaphot threads a few weeks ago. Lars Ellenberg