[sheepdog-users] stability and architecture
sirio81 at gmail.com
Fri Jan 16 16:51:39 CET 2015
2015-01-14 10:58 GMT+01:00 Corin Langosch <info at corinlangosch.com>:
> I'm thinking about switchting from ceph to sheepdog for backend storage of my vms. My main reasons are erasure coding
> support and local caching. I setup a test cluster (9.1 compiled from sources with zookeeper) of 6 machines, each having
> 1TB of sdd storage for sheepdog. Would you generally recommand using it in a production system with several hundrets of vms?
I suggest to test it first on your environment.
> As for monitoring, how can I get the cluster "health", something linke "ceph health" or "ceph -w" outputs? So basically
> which nodes are down and- how many (which) objects need recovery? I guess the first one could not be output as there's
> not such concept of "registered" nodes as ceph has?
I don't know ceph.
'Dog cluster info' shows an "history" of the cluster.
A new line is generated each time a node join or leave the cluster.
'dog node recovery' show which node are recovering with a progress bar.
> Does sheepdog provide periodic data integrity checking (scrubbing/ deep scrubbing) or is it planned? Is data integrity
> checked when objects are assembled from their individual chunks?
> If I understand correctly sheepdog is distributing an image to any number of nodes. So if I have 1000 nodes parts of the
> image can be on up to 1000 nodes (not very likely but you get the point). Now if I have 4:2 redundancy only 2 of these
> 1000 nodes are allowed to fail so that the image is still accessible. Is there any way to limit the number of nodes used
> for an image? For example limit an image to 100 nodes, to reduce the possiblilty of failure/ downtime?
That also means that you can run the guest "only" on the 100 nodes.
I don't thing it's possible do it.
> Afaik sheepdog uses the consistend hashing algorithm to choose which node should contains which parts of an image.
> Inside the node the same is done for the individual disks (in case of multiple disks per sheep setup). I wonder how
> sheepdog handles different disk sizes here? What happens if a disk runs full
A disk should never get full because the are used in proportion.
The only thing that may unbalance it is a disk fail.
If you didn't use --enable-diskvnodes option when building sheepdog,
the content of the broken disk is replicated on the same node without
triggering a cluster recovery.
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