On Tue, May 2, 2017 at 12:20 AM, Gandalf Corvotempesta <gandalf.corvotempesta@xxxxxxxxx> wrote:
It can be done. We just need to find time to do this.2017-05-01 20:43 GMT+02:00 Shyam <srangana@xxxxxxxxxx>:
> I do agree that for the duration a brick is replaced its replication count
> is down by 1, is that your concern? In which case I do note that without (a)
> above, availability is at risk during the operation. Which needs other
> strategies/changes to ensure tolerance to errors/faults.
Oh, yes, i've forgot this too.
I don't know Ceph, but Lizard, when moving chunks across the cluster,
does a copy, not a movement
During the whole operation you'll end with some files/chunks
replicated more than the requirement.
Replace-brick as a command is implemented with the goal of replacing a disk that went bad. So the availability was already less. In 2013-2014 I proposed that we do it by adding brick to just the replica set and increase its replica-count just for that set once heal is complete we could remove this brick. But at the point I didn't see any benefit to that approach, because availability was already down by 1. But with all of this discussion it seems like a good time to revive this idea. I saw that Shyam suggested the same in the PR he mentioned before.
If you have a replica 3, during the movement, some file get replica 4
In Gluster the same operation will bring you replica 2.
IMHO, this isn't a viable/reliable solution
Any change to change "replace-brick" to increase the replica count
during the operation ?
--
Pranith
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