[Xen-users] How can I uniquely identify my disk in guest OS on Xenserver?

[neo3 matrix <neo3matrix@xxxxxxxxx>]

Hi all,

I have installed RHEL6 as guest OS on Citrix Xen Server. After installation of OS, I can see disk names as /dev/xvda, /dev/xvdb instead of traditional convention like /dev/sda, /dev/sdb on guest OS.

Generally, on physical machines, in /proc/scsi/scsi file, we get a unique entry for every disk connected to the system. For e.g. string "scsi02:00:00:01" indicates that this disk is connected to the machine via Host=2, Channel=00, Id=00 Lun=01. This helps me in my project to uniquely identify each and every disk in scenarios where many times after reboot OR in SAN boot cases OR in some Disaster Recovery procedures, disk names might change from say /dev/sda to /dev/sdb after reboot. But, this Host:Channel:ID:Lun combination remains same for every disk and I can uniquely identify the disks though their /dev/sd* names have changed.

For my project, on Citrix Xenserver, I need to know the unique disk location for such Xen guest OS devices by which I can easily identify disks across the reboots for the above mentioned cases. 

So, I have couple of questions on this front. Please help me out or guide me for the same.

1. As /proc/scsi/scsi don't have such entry for /dev/xvdX type disks, do we have similar mechanism in Citrix XenServer to identify our guest OS disks uniquely?

2. This question is rather a continuation of previous one. While searching answer for above question, I found that for every /dev/xvdX disk, a unique device entry is present in /sys/block/xvdX/ directory in the format "vbd-XXX", for example, vbd-768, vbd-832, etc.
Here, vbd stands for Virtual Block Device. 
But what is the significant of the numbers 768, 832 ,etc.? How these are generated? Are they indicatingsomething like Host:Channel:Id:Lun? Can I trust these numbers to distinctly identify my disks? Are these numbers differ from one guest OS to other OR depend on Xenserver configuration?

Please suggest me some answer on this front. 

Thanks in advance.

Regards,
Neo

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