GPFS guarantees that only one node will write to a linux block device
using disk leases. 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
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