MSL6030 / 1 LTO2 + Arcserve & compression problem

[Chris V.]

Hi,

I'm currently having compression problems with the following config:
MSL6030 with 1 LOT2 (up-to-date firmware).
Arcserve 11.1 + SP1 + Device Patch 3.
Problem I have : some time the compression works, sometimes not and that on the same daily job (for instance, the compression did work on Monday night, when it didn't on Tuesday night).

I actually use Hardware compression and not software compression.

I haven't found anything obiousvly wrong on any part on the chain, I'm therefore retrieving information on the devices as well on Arcserve.

Any input will be welcome,

Chris

[Leon Rosier · Accepted solution]

The Ultrium drives use adaptive data compression. this might be the reason for the behaviour. Below you will see a statement about this.

"Things have moved fast in the storage industries and a range of multimedia file types are now commonly used which are already compressed. Examples of this include jpeg and mpeg formats. Since the files are already compressed, the hardware compression in the tape drive can no longer compress the files any further and in the worst cases can actually increase the size of the file by up to 5%.

In the worst case if you are backing up on which all data is pre-compressed (perhaps on a video editing machine, ftp server with compressed files), you will achieve more capacity on tape by disabling the hardware data compression*.

* The Surestore Ultrium 460,230, and 215 products feature adaptive data compression that will automatically monitor and engage/disengage the data compression when it is efficient to do so, so no change would be required. "

Leon

[Chris V.]

Hi Leon,

I read this, and would totally if the result would be always bad, and it's not the case.

Also, I do not have that much pre-compress files, I mainly have MS Office doc + SQL backup.

Thanks,

Chris

[Leon Rosier]

The Ultrium drives also make use of adaptive tapespeed totry to keep the drive in streaming mode. I can imagine that if the data throughput to the drive is too low, the drive also switches off compression. This however i am not sure about.
I think you also can check the compression function with HP library and tape tools.
Stop the Arcserve services and run L&TT.

Leon

[Chris V.]

Hi Leon,


From support call open with HP, it appears that problem may be with Arcserve (LTO seems to properly compress when used with LT&T).

It even seems that compression on a LTO drive can simply not be set off.

thanks for your help,

Chris

[josemaria cr]

Hi,

Be sure that the fw of your drive is supported by CA.
Check this in:
http://supportconnectw.ca.com/public/storage/infodocs/basb111win/basb111win_cdl.asp

jmc