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Home > Archive > Data Storage > March 2005 > DLT IV not reaching full capacity
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DLT IV not reaching full capacity
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| Dean Pearson 2005-03-08, 5:45 pm |
| I have a DLT 7000 with brand new Sony DLT IV tapes and when I backup
about 60G from several directories using tar on FreeBSD
5.2.1-RELEASE-p13 I can only ever get 45G out of the tape before it
falls over with:
Total bytes written: 48194365440 (45GB, 3.6MB/s)
/usr/bin/tar: /dev/sa0: Wrote only 0 of 10240 bytes
/usr/bin/tar: Error is not recoverable: exiting now
Prior to the tar command I collate a file full of sockets and FIFO
files which I pass to tar in a exclude-from argument, so I would not
imagine it to be a file to cause the premature end.
I have tried several SCSI cables and several SCSI cards, I have tried
many tapes and still I seem to hit this limit. Does anyone have any
ideas?
Kind Regards,
Dean
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| Rob Turk 2005-03-09, 7:45 am |
| "Dean Pearson" <dean@p-c-s.com.au> wrote in message
news:1110321796.779597.208780@o13g2000cwo.googlegroups.com...
>I have a DLT 7000 with brand new Sony DLT IV tapes and when I backup
> about 60G from several directories using tar on FreeBSD
> 5.2.1-RELEASE-p13 I can only ever get 45G out of the tape before it
> falls over with:
>
> Total bytes written: 48194365440 (45GB, 3.6MB/s)
> /usr/bin/tar: /dev/sa0: Wrote only 0 of 10240 bytes
> /usr/bin/tar: Error is not recoverable: exiting now
>
> Prior to the tar command I collate a file full of sockets and FIFO
> files which I pass to tar in a exclude-from argument, so I would not
> imagine it to be a file to cause the premature end.
>
> I have tried several SCSI cables and several SCSI cards, I have tried
> many tapes and still I seem to hit this limit. Does anyone have any
> ideas?
>
> Kind Regards,
> Dean
You get what you paid for. A DLT-7000 is 35GB native, minus some tar and
tape handling overhead you can expect about 32GB or so available. With 45GB
on tape you are getting 1.4:1 compression out of the drive. Nothing wrong
with your system.
Rob
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| 1.4:1 is about typical for a full system backup. The 2:1 marketing
figure applies to text files (sometimes.) With some files you can get
higher compression factors (rarely), with uncompressible files (e.g.
JPEG, MPEG or .gz) you'll even get less than 1:1 - in which case it
makes sense to turn compression off.
Ralf-Peter
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| Dean Pearson 2005-03-10, 2:45 am |
| Many thanks for your replies.
After logical thought regarding compression it makes sense to me now.
My full system backups are laden with binary files so thanks again.
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