[Gluster-users] Copy files from brick folders.

[Vijay Bellur]

On 12/07/2013 02:49 AM, wkmail wrote:
> I've googled this but didn't really see it addressed. Most posts discuss
> cleaning up after a split brain, etc.
>
> In a simple Replication setup, is there any problem with copying files
> from one of the ACTIVE bricks directly rather than going through the
> client mount.
> Does it affect gluster specific locking/healing/writing if the file
> involved is a large log file that may have data sent to it during the copy.

gluster operations like locking/healing etc. do not get affected by 
reads that happen from the bricks directly. However, you can do that 
only if you do not care for consistency of the data. For example, if a 
file is being self-healed, there is no guarantee on what the response 
would be to a read operation performed from the brick directly. Doing 
the same read operation over the mount point would guarantee that the 
right data is returned back to the application.

>
> I understand that files should only be modified via the client mount,
> but in a pure read situation such as a backup, keeping that traffic off
> the mount network would be an advantage.
>

If there is no write activity (either application driven or gluster's 
maintenance operations like self-heal, rebalance), then reading from the 
bricks might be fine. Since these operations are asynchronous in nature 
and since most applications are not written to be aware of the 
implications of loose consistency, the recommended method is to perform 
all reads through a gluster client stack.

Regards,
Vijay