On 12/17/2014 03:49 PM, Gregory Farnum wrote:
On Wed, Dec 17, 2014 at 2:31 PM, McNamara, Bradley
<Bradley.McNamara@xxxxxxxxxxx> wrote:
I have a somewhat interesting scenario. I have an RBD of 17TB formatted
using XFS. I would like it accessible from two different hosts, one
mapped/mounted read-only, and one mapped/mounted as read-write. Both are
shared using Samba 4.x. One Samba server gives read-only access to the
world for the data. The other gives read-write access to a very limited set
of users who occasionally need to add data.
However, when testing this, when changes are made to the read-write Samba
server the changes don’t seem to be seen by the read-only Samba server. Is
there some file system caching going on that will eventually be flushed?
Am I living dangerously doing what I have set up? I thought I would avoid
most/all potential file system corruption by making sure there is only one
read-write access method. Thanks for any answers.
Well, you'll avoid corruption by only having one writer, but the other
reader is still caching data in-memory that will prevent it from
seeing the writes on the disk.
Plus I have no idea if mounting xfs read-only actually prevents it
from making any writes to the disk; I think some FSes will do stuff
like defragment internal data structures in that mode, maybe?
-Greg
FSes mounted read-only still do tend to do things like journal replay,
but since the block device is mapped read-only that won't be a problem
in this case.
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