On Fri, 2014-08-15 at 13:45 +0200, Lars Marowsky-Bree wrote:
On 2014-08-15T13:39:45, steve
wrote: Other setups use it: http://sigterm.sh/2014/02/highly-available-nfs-cluster-on-debian-wheezy/
But that's not what they are doing. They are only mounting it once; with drbd (in normal configuration) it's only possible to write to the device once anyway, so no-concurrent mount would be possible anyway. Ok, I see: they are using fail over only? Presumably they will have only one node up at a time. Is that what you term local file system? Or is that something else? It's as clear as mud over here, sorry!
Right. A traditional "local" file system can only be mounted on one node at once without crashing.
In our case, we have drbd primary:primary with the data mounted on both nodes at the same time. Is it that configuration which cashes ext4?
Yes. This does not work and causes data corruption and crashes.
With ocfs2, it's fine. It still works though, even if we disable one of the nodes. We have only old hardware so it would be pointless having ext4 nodes with only one active at a time: we may as well go back to our single file server.
I'm not sure this holds. There's a penalty needed for syncing and locking. Have you benchmarked if a single node is really slower than two? Especially a write-heavy workload probably won't, and it'll go very much downhill if you have metadata-intensive jobs (e.g., creating/deleting/stating lots of files/directories).
The main reason for HA is, well, availability, not performance, thus going back to a single server is likely worse than this anyway.
That's our main reason too. Mainly for peace of mind: we can fix the file server that's failed whilst everyone can still work. If we go back to our old single file server, if that goes down nobody can do anything. Maybe that's not what ocfs2 is about, but if it keeps us working then any technical explanation is worthless to us.
Regards, Lars
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