Citrix XenServer and DR

Assuming your storage is capable of replication, a bunch of VMs could be happily replicated to an alternate location, where you can start them on will (and on crisis, most likely).

This procedure, in theory, is rather simple. I have discovered that it is less so, especially if your system goes into testing once a while.

This leaves some “memories” with Citrix XenServer, as well as the underlayer OS.

The forums show examples of how to handle iSCSI re-attach, so I am adding here hot to handle fiber channel re-attach operation as well, especially if you’re using multipath.

Grab the SCSI ID

The SCSI ID is very important, as it is he basic identified of the LUN:

xe sr-proble type=lvmohba 2>&1

This will show a section (XML-like) under “SCSIid” containing the device’s SCSI ID. Also – grab the UUID of the device, as XenServer assigns. You could do this with:

xe sr-probe type=lvmohba device-config:SCSIid=<Enter SCSI ID here>

Introduce the Device

The system needs the device introduced. For that we’ll use the above captured UUID:

xe sr-introduce uuid=<Enter the UUID obtained before> shared=true typb=lvmohba namb-label=”Imported SR”

Keep the UUID returned by this command. I will reference to it as “SR UUID”

Create PBD for each host in the pool

This should be performed for each host, based on the UUID of all hosts:

xe pbd-create sr-uuid=<Enter the SR UUID obtained before> device-config=SCSIid=<Enter SCSI ID> host-uuid=<Enter UUID of host>

The result value, for each host, is the pbd UUID for that specific host. pbd is a physical Block Device, meaning – the “connection” of the Storage Repository (which is pool-wide) to the specific host.

Plug PBDs

For each of the pbd UUID obtained above, run the following command to plug it in:

xe pbd-plug uuid=<pbd UUID as obtained above>

That should be all.

For ease of repeat, below is a script to perform these exact actions automatically. It assumes one (1) unallocated LUN at the beginning of the process. It will probably behave differently for more than one.

#!/bin/bash
SCSIID=`xe sr-probe type=lvmohba 2>&1 | grep -A1 SCSIid | grep -v SCSIid | grep -v vendor | tail -1 | awk '{print $NF}'`
echo "scsi ID: $SCSIID"
UUID=`xe sr-probe type=lvmohba device-config:SCSIid=$SCSIID | grep -A1 UUID | grep -v UUID | grep -v Devlist | head -1 | awk '{print $NF}'`
echo "SR UUID $UUID"
SRID=`xe sr-introduce uuid=$UUID name-label="Imported SR" shared=true type=lvmohba`
echo "SR UID: $SRID"
HOSTID=`xe host-list  | grep uuid | awk '{print $NF}'`
PBDID=""
for i in $HOSTID
do 
   PBDID="$PBDID `xe pbd-create sr-uuid=$SRID device-config:SCSIid=$SCSIID host-uuid=$i`"
done
for i in $PBDID
do
   xe pbd-plug uuid=$i
done