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Re: MSL6060 - Checking if compression is on.

 
Mark Bly
Regular Advisor

Re: MSL6060 - Checking if compression is on.

David,

Typing 'up' took us to the correct screen.

We thought that the first screen that appeared was the top level.

The system that we are using for the tests is running HP-UX 11i.
The library is connected to the SAN via a Brocade switch.

I am a bit worried that L&TT picked up the controllers on our XP512. Can it cause any problems?


Many thanks for all your help.


Mark


Remember to think before you react................but always make sure there is still time to react
David Ruska
Honored Contributor

Re: MSL6060 - Checking if compression is on.

> I am a bit worried that L&TT picked up the controllers on our XP512. Can it cause any problems?

LTT parses the kernel version of the ioscan (i.e. it doesn't rescan the system), and looks for SCSI/FC devices that it supports. It lists the 'other devices' it finds, but you cannot select them.

When it finds a tape library, it uses the SCSI read element status information to associate any drives on the system with the correct library.
The journey IS the reward.
Mark Bly
Regular Advisor

Re: MSL6060 - Checking if compression is on.

David,

Sorry to return to a previous thread but we have just carried out our first proper full weekly backup using the tape library.

We used one of the Ultrium 460 drives and backed up one of our development systems.

System:
HP-UX 11i attached to XP512

Total Data backed up:
262.41 GB

Length of backup:
8 hours 17 minutes

No of Media used:
2

Backup software:
Omniback 4.1 with drive concurrency set to 5

Media:
HP Ultrium 2 tapes

As you can see we went onto two tapes. This happened at about 170GB.

I thought that Ultrium 2 tapes had a native capacity of at least 200GB. Surely we should have been expecting well over 300GB per tape (obviously not expecting the 2:1 compression capacity of 400GB)

This would seem poor for an Ultrium 1 drive with compression let alone an Ultrium 2 drive.

What tool should I use from L&TT to figure out what is going on? It looks as if something is wrong with the library or drives.

Mark
Remember to think before you react................but always make sure there is still time to react
David Ruska
Honored Contributor

Re: MSL6060 - Checking if compression is on.

Mark,

Can you collect a LTT support ticket (select Support tool, select save to file) after the backup?

You can copy the support ticket to a windows host, and then view it with the windows version of LTT.

There is a data compression log which will show the MB from the host, and MB written to the tape.

I believe the log is cleared on a tape load, show it should represent one tape worth of data. On DLT drives the log is cleared on a tape unload, you you need to grab it before the tape is unloaded. I don't know if LTO is the same, or if it's still available after the tape is unloaded (I'll try it when I'm back in the office).

This log will show us if compression was enabled, what the compression ratio was, and how much data went on tape.
The journey IS the reward.
David Ruska
Honored Contributor

Re: MSL6060 - Checking if compression is on.

> Total Data backed up:
> 262.41 GB

> Length of backup:
> 8 hours 17 minutes

That's only 8.8MB/sec (including the time to swap tapes). The lowest streaming rate of the drive is 10MB/sec (native)

Were you just backing up to 1 drive at a time?

You might want to try the device performance tests to make sure the drive can stream. These are included in LTT, or available as separate utilities (hptapeperf). See this page for more info:
http://www.hp.com/support/pat
The journey IS the reward.
Mark Bly
Regular Advisor

Re: MSL6060 - Checking if compression is on.

David,

I just tried to run a support ticket against the drive using L&TT.
If I try to start the L&TT software with a backup running it does not detect the drive.

How can I keep the tape in the drive after a backup to get the compression report? (The library will automatically eject the tape when using omniback)

L&TT is definitely identifying these drives as Ultrium 2 but the performance still seems to be that of an Ultrium 1 (capacity of Ultrium 2 tape is less than 200GB)


Mark
Remember to think before you react................but always make sure there is still time to react
David Ruska
Honored Contributor

Re: MSL6060 - Checking if compression is on.

> I just tried to run a support ticket against the drive using L&TT.
If I try to start the L&TT software with a backup running it does not detect the drive.

In general, that's a limitation of in-band diagnostics through the OS. There's a workaround on windows (use the ASPI I/O option), but not on HP-UX.

> How can I keep the tape in the drive after a backup to get the compression report? (The library will automatically eject the tape when using omniback)

Yes, I realize there's a catch 22 here. I ran some tests over the weekend (on windows) to determine when the compression logs get cleared, but I haven't had time to look at the support tickets yet. Hopefully I'll get to that this evening.

The journey IS the reward.
David Ruska
Honored Contributor

Re: MSL6060 - Checking if compression is on.

> I ran some tests over the weekend (on windows) to determine when the compression logs get cleared...

It looks like the data compression log gets cleared as soon as the tape is unloaded (I was afraid of that).

I don't have a good answer on how to collect the compression information in a library drive. I will have to speak with a few folks and see if they have any brighter ideas.
The journey IS the reward.
Mark Bly
Regular Advisor

Re: MSL6060 - Checking if compression is on.

Closing old thread
Remember to think before you react................but always make sure there is still time to react