How to configure Citrix Xen for euroNAS SAN Cluster

Citrix Xen does not have multipath service nessesary to run activated per default.

Also multipath.conf needs to be configured prior using euroNAS – if this is not set – it is possible that you will experience data loss

euroNAS uses ALUA for communication with the server – this way the server can determine which part is active one.

Before activating multipath service under Xen please ssh to the Xen Server and add following lines to the /etc/multipath.conf file

for this you can use command nano
nano /etc/multipath.conf

device {
vendor "eSSM*"
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
features "1 queue_if_no_path"
hardware_handler "1 alua"
path_grouping_policy group_by_prio
failback immediate
rr_weight uniform
rr_min_io 100
path_checker tur
no_path_retry queue
prio alua
}

If correctly set you will see following output when multipath service is enabled and you issue the command
multipath -ll

26530353739643236 dm-0 eSSM_BIO,testdisk_0
size=500G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 alua' wp=rw
|-+- policy='round-robin 0' prio=50 status=active
| ´- 6:0:1:0 sdc 8:32 active ready running
´-+- policy='round-robin 0' prio=1 status=enabled
´- 6:0:0:0 sdb 8:16 active ready running

Should the FC ports used for server mirror be in separate zone?

Yes – ports used for server mirroring should be in separate zone.

Can I connect FC Ports for mirroring directly between the servers?

Yes – connecting FC ports used for mirror replication can be connected directly. Also connecting several several ports directly is supported – all ports will then be used in round robin mode providing you maximal performance.

Can I connect FC RAID Array as storage for SAN Cluster?

Yes – this will provide you 100% FC Solution. SAN Cluster will mirror both FC Arrays.

Can I use more than one FC Port for providing FC Storage to the clients?

Yes – you can use more than one port for providing storage to the clients. Thanks to ALUA communication all ports will be active, ports on the passive node will be shown as “Standby”.

If all active ports fail, other node will automatically take over and activate its ports.

You don’t nessesary need the same amount of ports on both nodes. You can have for example 2 or more active ports on master node and just one standby port on the slave node.

How should the clients be configured for the SAN Cluster?

euroNAS SAN Cluster uses for the communication with the FC initiators (clients) MPIO/ALUA. You have to make sure that your client is properly configured for multipath.

Windows server versions support multipath and need to be configured manually (MPIO service must be installed). VMware ESX and MAC XSAN will recognize multipath automatically.

Citrix Xen and Linux needs manuall configuration (check article “How to configure Citrix Xen for euroNAS SAN Cluster”)

Which FC HBAs are supported by SAN Cluster?

For use within SAN Cluster we currently support only QLogic FC HBAs.

On the client side all FC HBAs are supported.