11d with LTO4... bad performance, LTO3 tapes faster than LTO4?

[Joe_Bez]

Our HP LTO3 autoloader died out of warranty a few weeks ago, so it was time for an upgrade. We dropped in a HP Storageworks 1/8 G2 LTO 4.

It’s connected via LVD320 , on the old LTO3 autoloader we saw a local backup rate of around 5 to 5.5 GB a minute, But with the new LTO4 unit we only saw 3.5 to 4gb a minute at first.. But it now got even worst dropping right down to 2gb a minute!.

The 3.3tb Array is RAID5 and is SAS attached and is reporting zero problems, we have done defrags with Prefectdisk 10 and its reporting to be close to 100% performance.

The Server is used only by graphic designers, so the file types are all graphics types. So I know not to expect good compression, the best we see is 1.4 to 1 but when using the LTO4 tapes this has now dropped to 1.05 to 1 or on a few occasions worst than 1to1!

What I have noted is if we use LTO3 tape in the LTO4 auto loader we get better speed and better compression??!

I know this might be better on a HP storage forum, but I thought I’d start here in case Backup exec was doing anything odd..

Any ideas?

Windows Server 2003 sp2,
Backup Exec 11d rev 7170

Thanks

[teiva-boy]

It is more than likely that LTO-4 is too fast in your case.

The thing people forget to realize is that LTO3 and 4 are faster than what most hard drives can spit out.  Thus, the tape stops, rewinds, fast forwards, (meanwhile the buffers in the drive have filled) and writing resumes.
But again, if you cant meet the minimum sustained transfer rates, the buffer runs dry, and you get a shoe shine effect on the tapes and drive heads leading to premature failure, and slower backup rates.  

Is this a direct backup to tape, or are you staging this to disk, and doing a duplicate from disk to tape?

[Joe_Bez]

Its running a direct backup to tape, its all local no network drives, only running at night when the server is not in use.

The odd thing is if i setup a synesthetic test and use a dummy file creator and make say a 5gb files on the array , i get backup rates of over 5.5gb a min.

Would the drive shoe shining like this affect the compression? On the smaller/slower LTO3's we are seeing '1.4 to 1' but on the LTO4's is close to '1 to 1'. The thing i dont understand is the fact its got worst? The arrays are in a better state now after a lot of defraging but the data rate to an LTO4 tape is only 2gb/m where when the AutoLoader was new we saw up to 4gb.. what sustained rate do you think it needs to run smoother?

I have no errors but i wonder about the 320 SCSI card letting the side down...

The Array is a IBM EXP3000 in raid5 SAS connected but we are only running 7200rom SATA drives but i would have thought this would be quick enough.

[teiva-boy]

 The thing that is a burden to backups is small files.  Everything chokes on small files, but large contiguous files can be written like no other.

That said, if you had a separate disk volume, backing up to disk first, then doing a duplicate to tape is often faster than writing to tape directly.  Knowing the EXP3000, you should have it broken into smaller volumes anyways and not one large one.

It's not so much the array but more so the files you are backing up...

[Ken_Putnam]

Almost sounds like you may have a jiggy driver for the LTO-4

Have you tried the latest driver pack from Symantec?

Have you tried manufacturer drivers?