Gluster users - Oct 2015 - Unnecessary healing in 3-node replication setup on reboot

Am 16.10.2015 um 15:52 schrieb Ivan Rossi:
> looks like correct.
>
> during the reboot, if the vm write anything, at the end the files on
> #1 and #2 will be different from thos on #3 that was down. So healing
> is NECESSARY.
>
> Ivan
>
Ok, I see. :-/

To me this sounds like Gluster is not really suited for big files, like 
as the main storage for VMs - since they are being modified constantly.
Or am I missing something? Perhaps Gluster can be configured to heal 
only modified parts of the files?

Thanks,
Udo
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On 17 October 2015 at 00:26, Udo Giacomozzi <udo.giacomozzi at indunet.it>
wrote:
> To me this sounds like Gluster is not really suited for big files, like as
> the main storage for VMs - since they are being modified constantly.
>
Depends :)

Any replicated storage will have to heal its copies if they are written to
when a node is down. So long as the files can still be read/written while
being healed and the resource usage (CPU/Network) is not to high then it
should be transparent - that's a major  whole pint of a replicated
filesystem.

I'm guessing that like me, you are running your gluster storage on your VM
Hosts and you like me are a chronic tweaker, so tend to reboot the hosts
more than you should. In that case you might want to consider moving your
gluster storage to seperate dedicated nodes that you can leave up.

> Or am I missing something? Perhaps Gluster can be configured to heal only
> modified parts of the files?
>

Not that I know of.

ceph is pretty good tracking changes and only transferring them - heals
form a reboot only generally take a few minutes on my three node setup. But
it is a huge headache to set up and administer, and its I/O performance is
pretty bad on small setups (< 6 nodes, < 24 disks). But it scales really
well and really shines when you get into the hundreds of nodes and disks,
but I would not recommend it for small IT setups.


-- 
Lindsay
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