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Can't backup more than 200GB on LTO-2 tape with Brightstore Arcserve

Posted on 2009-04-06
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Since a while now every daily full backup writes data until it reaches approx. 202 GB and than it asks for a new tape. We use LTO-2 tapes and the Dell PowerVault 114T. The appropriate servcie in server 2003 was stopped and set to manual (removable storage) and the windows device drivers disabled. The second backup (two tape drive) works flawless with approx. data of 140GB. The error message displayed is W3828. Unable to find this or a blank media.
The tapes are new, and the tape drive as well. I formated a test tape but no change. The compression is turned on in Arcserve.
Any input is very much appreciated.
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Question by:goosegrapes
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6 Comments
 
LVL 12

Expert Comment

by:TapeDude
ID: 24081469
How compressible is the data? LTO 2 tapes have a native capacity of 200GB, so if you're trying to back up something that is already highly compressed - say, AVIs, JPEGs, zip files - you won't get any more than native capacity.
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by:L3370
ID: 24081492
First off, have you been able to get more than 200gb on these tapes and drives before?

are you sure you haven't reached the max capacity of the tape and drives?  While the tape allows for 200gb native/ 400 compressed, it may not be able to reach that cap with the current drives installed.  It also may be a problem with the data being compressed.  the amount of compression capable depends how compressible the data is. Sometimes you can reach 4:1 ratio, sometimes 1:1 is the max you can get.
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Author Comment

by:goosegrapes
ID: 24082910
Thanks for the commends.
I had successful backups before. They were in the area of 250GB. A lots of the files backed up are .tif, jpeg and autocad drawings. Is there an option were I can find the actual compress ratio?
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by:L3370
ID: 24082953
BE displays the compression ratio in the MEDIA tab. Click on the MEDIA tab and select one of your media sets.  It will then show the tapes in your media sets and the information related to it. Compression ratio should be one of the columns listed. If it isnt there click on the column and add it in.

Note: this indicates the compression ratio already applie to it. it does not indicate the maximum capability of compression.

If you are backing up a lot of files as listed above then do not plan on getting much out of it.  It is best practice to plan your backups around the native capacity of the tape, unless you've tested the backups extensively and know for a fact it will always hold enough in a compressed state.
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itprotocall earned 375 total points
ID: 24085593
compression ratio achieved will be reported in ARCserve activity log if the tape drive reports that back.
are you using software compression or hardware compression?

almost all modern tape drive have hardware compression built-in and if arcserve detects that i will use hardware compression by default.

and as stated in previous posts, the ratio of compression achieved depends a lot of on the format of the data being backed up. TIF and auto-cad drawings may not be that 'compressible'

if you are getting anything above 200GB in a 200/400 tape, that indicates compression is happening but the ratio is not something you expected.
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by:TapeDude
ID: 24085668
If you want to know how compressible your data is, you could try compressing a representative sample using winzip or 7zip. If you're only getting a few % decrease in size, then you know why you're not squeezing much more than the native capacity onto the tape.
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