[Linux-cluster] Redundant (multipath)/Replicating NFS

[isplist at logicore.net]

> If you have 2 NFS server you need replicated and failed over, you can
> use DRBD to replicate a virtual block device. You can have this in

I'm looking on the net about this and it looks interesting. I see that it is 
available as RPM's but I don't see it as being part of RHEL? Is this something 
that will run on one or more servers? I can't actually run anything on the NFS 
servers since they are embedded OS's on hardware. I;m using NAS servers 
offering up NFS shares from pools of RAID FC storage.

I'd like to use something like this for the web data that the web servers need 
access to. Your aggregator suggestion is what I've decided upon for the larger 
ongoing needs of media storage. 

Static web stuff as above is relatively easy to deal with using the right 
tools but I'm trying to figure out how to deal with large amounts of media 
data. Obviously, I don't want users to lose their pictures, videos, files, 
work, etc. 

What are your thoughts on even bothering to replicate when using RAID storage 
devices to begin with? They are highly reliable as it is, using 12 drives, 
hard to imagine a loss off data.
I have huge amounts of tape storage using robot libraries with multiple drives 
but still, that doesn't seem like the way to deal with the media. Setting up 
fully redundant storage seems to be a doubling of costs no matter how I cut it 
so I am at a loss on how to deal with media. 

Mike


> primary/primary mode with GFS on top, and you can then export the FS
> from both machines via NFS. If you use UDP NFS, you can have a floating
> IP address for the server that you fail over in case of a node failing.
> There may be a way to load balance NFS, too, but I've yet to see that
> actually work. If you are just failing over, you could run DRBD in
> standard mode without GFS. DRBD has heartbeat plugs.
> 
>> Is there any way of replicating NFS data in real time rather than as a
>> regular
>> backup, such as RAID1 for example, and be able to fail over to the second
>> path
>> or NFS IP should the first fail.
>> 
> DRBD is effectively RAID1 over TCP/IP.
> 
> Gordan
> 
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