I'm configuring a new SAN for a set of Ubuntu 18.04-based servers. Each of nodes can mount the ext4 formatted partition fine.
Being new to both multipath and iSCSI, I'm not sure if what I'm seeing is "normal". I'm having two problems so far.
When I create a file with
touch
, the other nodes do not see it. I'm used to some kind of delay with NFS mounted drives, but basically, the other nodes never seen it (i.e., I'm still waiting and I guess an hour has passed already).More worrying, is that when I list a copied file with
ls
ordu
the directory it is in, I get an error "Bad message". I looked around the Internet and it seems the solution is to unmount the drive and then usefsck
to check it. That is, data corruption might have occurred. However, on the computer I copied the file with (i.e., computer A), the file is fine. When Ils
it with another computer (i.e., computer B), I get this error.
In the management software of the SAN, I don't see any disk errors.
All of the servers and the SAN are connected to a single switch for a local network. They are physically close to each other -- they are in the same rack.
Are these two situations "normal"? If not, any suggestions on what I can do?
That is normal behavior for a non-clustered file system.
To use iSCSI SAN with Ubuntu compute servers, a clustered file system should be used.
You should probably learn more about GPFS, GFS2, Lustre, GlusterFS, and OCFS2 and use one of them on top of iSCSI SAN.
Edit: Good description of what’s going on can be found here:
https://forums.starwindsoftware.com/viewtopic.php?f=5&t=1392
ext is not a cluster-aware filesystem, so the moment a second node mounts it it will be corrupted. This is because there's no common block locking mechanism, which there is with a cluster-aware filesystem
Use a cluster-awre filesystem.
Um...
A SAN is not NFS. Unless you're using a shared/cluster filesystem, you can't just mount something ext4 onto multiple hosts.