Assign Snapshot the same physical device number on Host for Virtual Machine

if i understand you correctly you are trying to re-assign shapshots and want to make sure that HostID (LUN id) is always the same ?

I am using navicli commands, in a batch file, using -hlu switch that looks like this:

navicli -h [IP_address] storagegroup -addsnapshot -gname [storage_group_name]
-hlu 7 -snapshotname [snap_shot_name]

In either the windows or linux environments the physical device number assigned to the device (disk drive) appears to be assigned correctly (same as last assignment) but not in all cases. I am running these commands back to back adding multiple snapshots to the storage group at the same time. The linux environment does not complain about the physical device number assignment but does not always assign the same number as the last time the snapshot was assigned, but in the windows environment I will always receive two or three errors from the navicli commands that states that the hlu number has already been assigned. In that case the snap shot is not assigned to the storage group and I have to assign it manually.

It appears that both the linux and windows environments assign physical device numbers somewhat at random that I have no way of predicting. I have read about the admhost utility that has the ability to deactivate and activate luns after the assignment and this utility can be used to assign drive letters to the snapshot or luns that is being inserted into the storage group. The admhost utility only works in a windows environment so I can not use it on a linux host. I need the ability to assign the snapshot based on the physical device number to ensure that the snapshot always ends up with the same one, thus keeping the mapping of the physical devices to the virtual machine running on the host valid so the virtual machine will start after the snapshots have been removed, recreated and reassigned to the host.

Thanks very much for your help. I was not aware that once the snapshot was created it could be activated and deactivated repeatedly and still reside in the storage group.

I was under the impression that the snapshot had to be removed from the storage group, destroyed, recreated, placed back in the storage group then activated.

The snapshot basically servers as a place holder for the physical device once it has been assigned to the storage group and the attached server.

As in all things, thinking to much makes things to hard. I should strive to be more simple minded.

This was my first attempt with snapshots and the application I am dealing with is 24/7 and cannot go down for maintenance for any other reason. This is why I was taking a very conservative approach.

Thanks again