IMAGE FROM LUN (UNIT) TO LUN (UNIT) IN AN MA8000

[Carlos Sotelo_1]

Hi,

We need to change some older LUNs or UNITS in our MA8000 Storage SAN by some other LUNs with higher capacity. This LUNs are configured in RAID5 from the MA8000 with two HSG80 disk controllers and it actually has disks each with a capacity of 36 GB configured for RAID5 LUNs and will be replaced by disks of 72 GB configured equal as RAID5 LUNs. Sombody knows how I can achieve this task by coping or making an image from the old LUN to the new LUN, as posible in the MA8000 itself? this because the older LUNs have information recorded in, and no one of our servers boot from the MA8000 each one boots locally.

Any comentary is grateful welcome.

Thanks in advance.

[Mike Naime]

Sorry, but you can't do that with raidsets.

If you had a mirrorset that you wanted to copy, you can RUN CLONE in the HSG80. It basically ads a third member to the mirrorm and then breaks the member off into it's own LUN after the copy is complete.

What you will need to do is to present both LUNS to a sever and image them at the OS level.

Mike Naime

[Carlos Sotelo_1]

Thanks a lot, Mike:

I had read in the CLI HSG80 controller reference book that there is antoher command called ADD SNAPSHOT_UNITS wich is used to assign to a unit known as the source unit a snapshot unit wich takes a snapshot in time of the source unit. In wich cases is this command useful. We thoug that could be used in for this porpouse.

Greetings.

[Uwe Zessin]

Carlos,
a snapshot will not do what you want. You cannot use it to move data from one unit to another unit.

[Carlos Sotelo_1]

Thanks a lot.

OK. I agree with you both about all this.

Just to clear my doubts and increase in a little bit more my aknowlegment, and may be to implement it, could you just explain me in few words what I can do with the HSG80 CLI ADD SNAPSHOT_UNITS comand.

Regards.

[Uwe Zessin]

A snapshot is used to provide a so-called 'point-in-time copy' of your data.

On the HSG you first create a second storage set that will be used for temporary storage. After you have used the 'ADD SNAPSHOT_UNITS' command you will see another unit. It's contents look exactly like a copy of the parent unit. The reason is that the snapshot unit at first shares the same data blocks with the parent.

Now, imagine somebody writes to the parent - obviously that will overwrite data and change the contents of the snapshot unit, too. This is not what you want when you do a backup, for example.

In order to provide a consisten view of the snapshot unit, the HSG reads the old data from the parent and writes it into the temporary storage set that you have created. After that it updates the pointer table of the snapshot unit. Finally it writes the new data to the parent unit.

So, the snapshot unit looks like a stable copy of you parent unit except that you have not made a real copy with moving lots of GigaBytes around.

I hope that has cleared the confusion a bit.

For snapshots on the HSG you need two HSG80 controller modules, each with 512 MegaBytes of cache and ACS firmware cards with snapshot code (e.g. V8.7-1S).