library - SAN

[Kurt Beyers.]

Hi,

Suppose I have a small SAN environment: 2 HP-UX servers connected via fibre to a Brocade Switch. At the switch there is as well a connection to a VA7100 disk array and a small library E 2/20. If I do an ioscan on both the HP-UX servers, will I detect the DLT drives and robotic control of the library on both systems or do I have to configure it somehow? I know that in a normal environment you should create the device file for the robotic control yourself.

I'm just wondering how it works in the SAN.

Thanks,
Kurt

[Duncan Edmonstone]

If everythings set up OK, you *should* just see the tape drives from both servers. If you are on at least version 11.00 of the OS then simply adding the schgr driver to the kernel should allow you to identify the robotic picker. You do need to be careful with sharing the tape devices between the two servers though, as there's nothing built into the OS that prevents you trying to talk to a drive while the other system is using it - I know products like Omniback have functionality to resolve this kind of thing... what backup product are you using?

[Duncan Edmonstone]

I should also add that if you are using the same HBA(s) for access to the VA as you are for the disk, then you should make sure that you use swicthed fabric, rather than FC-AL.

HTH

Duncan

[Duncan Edmonstone · Accepted solution]

Kurt,

I guess your using Omniback, as I just saw your post in the Management Software section.

So if you want to backup a server straight over the SAN using omniback...

1. Don't try and use ATS - this isn't SAN-ready yet...
2. The robotics should all be controlled from one server (probably you cell manager).
3. When configuring the tape library, make sure the SCSI Reserve/Release box is NOT checked.
4. Define the tape drives in the library from every server which can see them on the SAN. e.g. if you have two drives, visible from two servers you set up four drives for the library - you then prevent concurrent access to these drives by setting up a common lock name (see point 6 below)
5. For the drives in the library make sure the SCSI Reserve/Release box is NOT checked, and Use Direct Library Access is NOT checked (in advanced options).
6. Set up a common lock name for each tape device in the library (again this is in the advanced options section)
7. If you have mulitple HBAs use only one path per tape drive, and distribute the drives across the HBAs. BUT don't forget the usual rules about not maxing out the bandwidth to tape drives, as this prevents streaming.
8. You'll also need to disable EMS monitoring for tape drives, as its not yet SAN-aware and chucks errors all over the place!


HTH

Duncan

[Michael Tully]

Hi Kurt,

The hard part about making this work is
making sure that you have it set up right
from the beginning. I cannot stress this
particular point enough. We have and 'N' class
(OBII cell manager) and 'L' class patched
into a Brocade switch. From there both
have access into both a EMC SAN and a HP
20/700 tape library.
If you do an ioscan you *SHOULD* see tape
drives and the tape library on both systems.
Do not under any circumstances use the
robotics on system B. Suggest you have the
cell manager and robotics controller on the
same server if possible, but not mandatory.
I've attached a couple of things here which
will help in setting up the robotics.
As Duncan has mentioned, in his posts, I agree
with the points 1-7 and partially 8. The
problem with 8, is that EMS does do ioscans
which tape libraries do not like..... The
problem with 'ioscan -fn' is that it tries
to discover hardware. Once it is found try to
use 'ioscan -fnk' instead. This reads out of
the kernel, not querying devices. Have a look at these links which has more information.

http://www.hp.com/cposupport/manindex/hpsurestor18469_eng_man.html
http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x55e2f715edc6d5118ff10090279cd0f9,00.html

HTH
-Michael

[Kurt Beyers.]

Duncan, Michael

Thanks for your clarifying answers. I've got one more question.

The two HP servers will be a MC ServiceGuard cluster, and one of the two nodes will be the OB cell manager (OB will run locally, not in a package). So for the packages I define the logical device by using there virtual hostname instead of the real node name. For the device file, I guess I just take the /dev/rmt/#m as it will be on both nodes as well. Or do I need to create the ATS configuration files (as stated in Chapter 2, page 46 of the OBII 4.0 Admin Guide) and use the /dev/rmt/st#m device files. They mention over there that the Direct Library Access should be enabled as well, but isn't this only necessary when OB itself runs in the cluster?

Thanks,
Kurt

[Duncan Edmonstone]

No, don't configure ATS - this is apparently still being tested by HP in a SAN fabric configuration. So as usual untested = unsupported. Keep checking with your HP contacts though as this could change any day.

HTH

Duncan

PS - Thanks for the points! You earned me my first Hat!

[Kurt Beyers.]

But will it work if I use /dev/rmt/#m as the device file to define the logical device. This device file isn't on the file systems of the package but on the local file system of the nodes.

something else about the licensing: if I only have 1 physical drive, I guess I only need one singe drive Unix license even if I have multiple logical definitions for that drive on different hosts?

Kurt

[Duncan Edmonstone]

Kurt,

Afraid I don't know the answer to you question on licensing...

With regards to the tape devices... as long as /dev/rmt/2m on Node A and Node B both actually point to the *same* tape device, thats fine (If they don't I'd consider using ioinit to re-order them).

HTH

Duncan

[Michael Tully]

Hi Kurt,

The license issue is this. One drive in
use equals one drive license in use. So
any backup that is expecting to start
will sit and wait in the status called
'Queueing' waiting for a drive license
to be freed. Once backup one is completed
the license is free for the backup in the
'queued' state to start.

HTH
-Michael