Il 21 mag 2016 08:38, "Kevin Lemonnier" <lemonnierk at ulrar.net> ha scritto:> Yeah, but healing a few MB shard takes a few second, so the VM is frozenfor a very small> amount of time. Without sharding, the VM is frozen as long as the wholedisk hasn't> been healed, which will take hours on big clusters.Which is the OS reaction to a locked storage? It's transparent or could lead to FS issue? What would happen if healing starts in the middle of a write, for example when MySQL flush to disks? Let's assume a 100gb image sharded (10mb) in a replica 3 on a 3 nodes cluster the image is split in 10.000 pieces, stored in all servers (replica 3) If a server goes down, the whole VM needs to be healed , thus the whole vm is locked Shard is useful on single brick failures, that could be avoided by using raid, non for server failure -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.gluster.org/pipermail/gluster-users/attachments/20160521/e9627d25/attachment.html>
> Which is the OS reaction to a locked storage?A It's transparent or could > lead to FS issue? > What would happen if healing starts in the middle of a write, for example > when MySQL flush to disks?In my experience the OS can't notice that, actually. The access to the disk won't fail, it'll just wait for the heal to finish before returning : your VM will freez. When the heal finishes the access will return correctly and everything will continue as if nothing happened. Might depend on the OS though, no idea how windows would react, but for Linux at least even hour long heals never caused any problem to the VM, except of course the fact that the VM froze and all services on it stopped responding during the heal. We didn't have sharding at first, and the behaviour is pretty much the same, but the heals take forever. -- Kevin Lemonnier PGP Fingerprint : 89A5 2283 04A0 E6E9 0111 -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: <http://www.gluster.org/pipermail/gluster-users/attachments/20160521/c85b9247/attachment.sig>