DAT/DDS tape backups...

[Joel Jaeggli]

On Fri, 30 Dec 2005, Angus MacGyver wrote:

<snip>

>
> [root at hostname data_backups]# du -sh *
> 19G     data
> 17G     data.tar.gz

Ok, so whatever you have in data is only compressible by 11% using gzip, 
it's entirely possible that the compression algorythm used by your tape 
drive actually end up making it larger.

> 1.9G    mail
> 494M    mail.tar.gz
>
> There is only actually 21G in the directories of data/ and mail/ and I
> kinda think i should be able to get 21G on to a tape with compression
> turned on...
>
>
> Whilst I am here, i can also say that it isn't the hardware, as i have
> another tape drive, a DDS-5 (36/72) that does exactly the same thing
> with these tapes..
>
> The tapes I am using are brand new, so should not have lost any
> capacity.
>
> This machine is a Fedora core 3, and some details below..
>
>
> [root at hostname ~]# uname -a
> Linux hostname.somewhere 2.6.12-1.1381_FC3smp #1 SMP Fri Oct 21 04:03:26
> EDT 2005 i686 i686 i386 GNU/Linux
>
>
> [root at hostname ~]# mt -v
> mt-st v. 0.8
>
> [root at hostname ~]# dump
> dump 0.4b39 (using libext2fs 1.35 of 28-Feb-2004)
>
>
> [root at hostname ~]# cat /etc/stinit.def
> # DDS-4 Guestimate
> manufacturer=COMPAQ model = "TSL-10000" {
> scsi2logical=0 can-bsr can-partitions auto-lock
> mode1 blocksize=0 density=0x26 compression=0      # 20GB noC
> mode2 blocksize=512 density=0x26 compression=0    # 20GB + Compression
> mode3 blocksize=512 density=0x26 compression=1    # 20GB no Compression
> mode4 blocksize=0 density=0x26 compression=1 }    # 20GB + Compression
>
>
> Can anyone shed some light on this please???
>
> Regards
> AM
>
>
>

-- 
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Joel Jaeggli  	       Unix Consulting 	       joelja at darkwing.uoregon.edu
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