Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

  • Congratulations Westi on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!

Tape Capacity

Status
Not open for further replies.

mot98

MIS
Jan 25, 2002
647
CA
Hi All,

Running BE 8.6 on NT 4.0 here. I have a seagate Python Autoloader tape drive. I just recently bought some new Sony DDS3 tapes. When I run a backup with these tapes I am getting different capacities out of them. On the one tape it backed up 15GB before moving to the next tape, and then the next one backed up 11GB before it moved on.

What is going on here?? These tapes should be able to backup 24GB compressed should they not?

mot98
[cheers]

"Victory goes to the player who makes the next-to-last mistake."
- Chessmaster Savielly Grigorievitch Tartakower (1887-1956)
 
24GB per tape is with 2:1 compression. Most backups usually get 1.6:1 compression. So your 12/15GB per tape is about right.

 
Why then do you get such a variation from tape to tape...On one of my tapes I actually got 19GB...and then on another only 11GB...I can understand a small difference..but 8GB??? mot98
[cheers]

"Victory goes to the player who makes the next-to-last mistake."
- Chessmaster Savielly Grigorievitch Tartakower (1887-1956)
 
Are there any bad blocks on any of the tapes? Have you tried to format the tapes to see if that makes a difference?

-SQLBill
 
They are brand new tapes so I find it hard to believe that there would be any bad blocks on them already. I am going to try and format them and see what capacity I get then.

mot98
[cheers]

"Victory goes to the player who makes the next-to-last mistake."
- Chessmaster Savielly Grigorievitch Tartakower (1887-1956)
 
The uncompressed capacity of the tape is 12 GB.
Be happy for everything more you get then that.
In our installation the average compressing rate on all our Windows data is 1,6 - 1,8 : 1 (based on 1 TB data mixed from anything from small files, file-servers, DataWarehouse, Ghost images, Exchange, web and SQL servers)

But we have a lot of data that compresses 1:1 and also data that compresses 16:1 (some even more)

Mostly it depends on the data. A 200 GB SQL databases containing nothing but "space" can be compressed to almost nothing.
If it's a DVD movie be happy if you get 1:1 and not 1:0,9 (have seen that one)
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor

Back
Top