Is the tape full?

[BillyL]

Setup:
Backup Exec 7.2
Device: HP SureStore DAT8
Compression: Hardware (if available, otherwise none)

Weekday backup job:
Differential
Runs Mon-Thurs, tape is changed each week
Append, Overwrite if no appendable media is available

Media set properties
Overwrite protection period: 4 days
Append period: Infinite

Here's the problem: I am running Weekday differential backups Monday - Thursday on a single tape which I change every week. Beginning a few weeks ago on about the Wednesday or Thursday backup I would be prompted to insert an appendable tape because the current tape is overwrite protected. I was thinking that the tape was filling up so last week I did a Quick erase on the tape and relabled it. By doing this I believe that I am wiping the tape clean and starting with in effect a new, blank tape.

Last week it ran fine all four days. Here are the numbers for each day:
Monday: 1,050,773,563 bytes
Tuesday: 986,313,444 bytes
Wednesday: 1,097,974,721 bytes
Thursday: 1,250,996,881 bytes
Total bytes: 3,498,376,509

This week it failed (see prompt above) on the Thursday backup. Here are the numbers:
Monday: 1,121,424,880 bytes
Tuesday: 1,242,333,465 bytes
Wednesday: 1,253,963,259 bytes
Total bytes to date: 3,617,721,604
Thursday: 950,137,329 bytes (that is where it stopped and waited for new media)
Total: 4,567,858,933

So here is my question: Is the tape filling up? This drive is supposed to have 8GB capacity w/compression.

My Friday backups which are Normal have backed up over 5GB on some weeks.

Any ideas??? Do I need to purchase a new drive? From my understanding, I cannot chain two dissimilar drives together (I have an HP SureStore 6000).

Thanks!

 

[2ffat]

Manufacturers give the optimal compression rate for their tapes. It is unlikely that you can truely acheive this in real life. Different methods of compression can produce different results. For example, software compression may not compress the same way as native hardware compression.

Files that are already compressed cannot be compressed any further. Some servers compress files automatically to save space. Programs like PK-Zip, WinZip, et. al. compress files about as efficiantly as possible. Backup programs cannot compress these files any further so they are copied as is.

Another factor is the type of files you are backing up. Some data base files and executables won't compress as much as text files, for example.

I've found that my Backup Exec compresses files about 1.3:1 to 1.6:1 (at best). Never do I see a 2:1 compression.

A couple of things to look at are what type of files are you backing up and the compression method (software vs. hardware). If you can change compression methods, try that to see if you get any better results.


James P. Cottingham

http://www.ivcusa.com