[Linux-cluster] How do you HA your storage?

[urgrue]

But, how do you get dm-multipath to consider two different LUNs to be in 
fact two paths to the same device?
I mean, normally multipath has two paths to one device.
When we're talking about san-level mirroring, we've got two paths to two 
different devices (which just happen to contain identical data).

On 30/4/11 11:47, Kit Gerrits wrote:
> With dual-controller arrays, dm-multipath  keeps checking if the current
> device is still responding and switches to a different path if it is not.
> (for examply, by reading sector 0)
>
> With SAN failover, you may need to tell the secondary SAN LUN to go into
> read-write mode.
> Unfortunately, I am not familiar with tying this into RHEL.
> (also, sector 0 will already be readable on the secundary LUN, but not
> writable)
>
> Maybe there is a write test, which tries to write to both SANs
> The one which allows write access will become the active LUN.
>
> If you can switch your SANs inside 30 seconds, you might even be able to
> salvage/execute pending write operations.
>
>
> Regards,
>
> Kit
>
> -----Original Message-----
> From: linux-cluster-bounces at redhat.com
> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of urgrue
> Sent: zaterdag 30 april 2011 11:01
> To: linux-cluster at redhat.com
> Subject: [Linux-cluster] How do you HA your storage?
>
> I'm struggling to find the best way to deal with SAN failover.
> By this I mean the common scenario where you have SAN-based mirroring.
> It's pretty easy with host-based mirroring (md, DRBD, LVM, etc) but how can
> you minimize the impact and manual effort to recover from losing a LUN, and
> needing to somehow get your system to realize the data is now on a different
> LUN (the now-active mirror)?
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