On Tue, Dec 22 2015, Tejas Rao wrote: > GPFS guarantees that only one node will write to a linux block device > using disk leases. Do you have a reference to documentation explaining that? A few moments searching the internet suggests that a "disk lease" is much like a heart-beat. A node uses it to say "I'm still alive, please don't ignore me". I could find no evidence that only one node could hold a disk lease at any time. NeilBrown > Only a node with a disk lease has the right to submit > I/O and disk leases expire every 30 secs and needs to be renewed. Lustre > and other distributed file systems have other ways of handing this. > > Using md devices in a shared/clustered environment is something not > supported by Redhat on RHEL6 or RHEL7 kernels, so this is something we > would not try in our production environments. > > Tejas. > > On 12/21/2015 15:47, NeilBrown wrote: >> On Tue, Dec 22 2015, Tejas Rao wrote: >> >>> What if the application is doing the locking and making sure that only 1 >>> node writes to a md device at a time? Will this work? How are rebuilds >>> handled? This would be helpful with distributed filesystems like >>> GPFS/lustre etc. >>> >> You would also need to make sure that the filesystem only wrote from a >> single node at a time (or access the block device directly). I doubt >> GPFS/lustre make any promise like that, but I'm happy to be educated. >> >> rebuilds are handled by using a cluster-wide lock to block all writes to >> a range of addresses while those stripes are repaired. >> >> NeilBrown > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html
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