[Linux-cluster] SCSI Reservations & Red Hat Cluster Suite

[Ryan O'Hara]

Jeff Macfarland wrote:
> Nice overview. Wish I had this a few weeks ago :-)
> 
> I am curious as to why LVM2 is required?

The reason for the cluster LVM2 requirement is for device discovery. The 
scripts use LVM commands to find cluster volumes and then gets a list of 
devices that make up those volumes. Consider the alternative -- users 
would have to manually define a list of devices that need 
registrations/reservations. This would have to be defined on each node. 
What make this even more problematic is that each node may have 
different device names for shared storage devices (ie. what may be 
/deb/sdb on one node may be /deb/sdc on another). Furthermore, those 
device names could change between reboots. The general solution is to 
query clvmd for a list of cluster volumes and get a list of devices for 
those volumes.

> With simple modification of the
> scsi_reserve (and maybe fence_scsi), using an msdos partitioned disk
> seems to work fine.
> 
> This is only in testing but I haven't seen any issues as of yet.
> 
> Ryan O'Hara wrote:
>> Attached is the latest version of the "Using SCSI Persistent
>> Reservations with Red Hat Cluster Suite" document for review.
>>
>> Feel free to send questions and comments.
>>
>> -Ryan
>>
>