Hi Dejan,
On 20/12/2007, at 7:50 PM, Dejan Muhamedagic wrote:
Hi,
On Thu, Dec 20, 2007 at 05:48:10PM +0900, Trent Lloyd wrote:
Hi All,
I have recently setup a 2-node iSCSI fail-over array backed onto
shared SAS MD3000 storage.
How is this thing connected: is it iSCSI or SAS?
Sorry that wasn't clear - to the nodes running heartbeat they are
connected via SAS - they then serve them up via iSCSI.
I have everything (including RDAC) working fine on my Debian Etch
nodes - however I am curious if it is possible to get heartbeat to
demote itself if it loses access to the disks - I am not sure if I am
missing something but it seems if the disks start failing on a node
there's no mechanism to cause it to failover.
The kernel should take care of that. If the computer hangs or
crashes, there won't be heartbeat and, after a successful fencing
operation (you do have a stonith device, right?), a failover will
occur. You can also configure a watchdog. Or did I misunderstand
your question?
I would expect that if a single disk array disappears - the machine
shouldn't hang - only processes that were depending on those would
hang. The same disk array does not contain the root array or anything
like that - only the data partition.
Is there anything to do this currently?I can't see anything. I
figure
it would be possible to write a plugin to monitor the dm-multipath
stuff - is this a reasonable approach?
It's been a long time since I used that. How can one monitor
dm-multipath? Isn't it fault tolerant?
It is, but I'm talking in a situation where for some reason both paths
are lost. I know this seems kinda paranoid but it just seemed like a
reasonable thing to do to me.
Example output:
filer2:~# multipath -ll
mpath0 (360019b9000b6b68e00001c2a46e8e656) dm-0 DELL ,MD3000
[size=1.9T][features=0][hwhandler=1 rdac]
\_ round-robin 0 [prio=3][enabled]
\_ 2:0:0:0 sdd 8:48 [active][ready]
\_ round-robin 0 [prio=0][enabled]
\_ 1:0:0:0 sdb 8:16 [active][ghost]
So we could parse or write some API that makes the same call this make
to make sure that the mpath0 has at least 1 active working path.
Regards,
Trent
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