InformatiQ

The setup

• storage node STOR01 @ x.x.x.1
  • based on openfiler [www.openfiler.com]
  • 2 NICs
• processing node PROC01 @ x.x.x.2 and y.y.y.1
  • Centos 5
  • XEN
  • open-iscsi-initiator 
  • 2 NICs
• both nodes are connected back-to-back through x.x.x.0 subnet
• STOR01 has several ISCSI targets exposed 
• PROC01 connectes to the thargets exposed by STOR01
• Xen domUs use thos iscsi targets as disks 
  • disk = [ 'phy:/dev/sdh,hda,w'] #/dev/sdh is the iscsi target 

The problem

i had all my targets connected to PROC01, Xen domains onf files written, domains started successfully and OS was installed.

Now after a reboot of PROC01 all is lost, no xen domU started...

why? simply because the iscsi targets were linked to different device files, e.g. instead of /dev/sdh it was on /dev/sdi

now how do i make sure that doesn't happen again?

• In Debian/Ubuntu the iscsi target is located at /dev/mapper/$iqn/disk
• in Centos iscsi target is located at /dev/disk/by-path/ip-$ip-iscsi-$iqn
• those files are symlinks to /dev/sd? , now either you can use those symlinks script something to modify the xen conf files before starting the domUs