On 09/22/10 11:22, Moazam Raja wrote:
Hi all, I have a ZFS question related to COW and scope.
If user A is reading a file while user B is writing to the same file,
when do the changes introduced by user B become visible to everyone?
Is there a block level scope, or file level, or something else?
Thanks!
Assuming the user is using read and write against zfs files.
ZFS has reader/writer range locking within files.
If thread A is trying to read the same section that thread B is writing
it will
block until the data is written. Note, written in this case means
written into the zfs
cache and not to the disks. If thread A requires that changes to the
file be stable (on disk)
before reading it can use the little known O_RSYNC flag.
Neil.
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