Date: Wed, 16 Mar 2005 14:50:02 +0100 (CET) From: Ludo Koren <lk@tempest.sk> To: xfb52@dial.pipex.com Cc: freebsd-questions@freebsd.org Subject: Re: Backup on DDS-4 tapes Message-ID: <200503161350.j2GDo2fR014888@lk.tempest.sk> In-Reply-To: <42381DF3.5060906@dial.pipex.com> (message from Alex Zbyslaw on Wed, 16 Mar 2005 11:52:19 %2B0000) References: <200503140938.j2E9c2EM024428@lk.tempest.sk> <42370004.5060506@dial.pipex.com> <200503160953.j2G9rjKR003358@lk.tempest.sk> <42381DF3.5060906@dial.pipex.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> Ludo Koren wrote:
>> It doesn't help either... The result is the same.
>>
>>
> Just to check I'm understanding your problem correctly --
> you're expecting to write much more data to the tape than is
> actually being written.
That's right. I suppose that 54GB of data could fit on 2 40GB tapes...
> If that's correct, then there's a couple things I can think of:
> 1) Your tape drive isn't doing hardware compression. Check the
> manual and see if there are any dip switches you need to set.
> (Make a note of how they're set before you change anything, so
> you can go back to what you had originally!).
I'll check this
> When you say the result is the same, if it used exactly the
> same number of tapes (down to the decimal point) then that
> definitely suggests that your tape drive is not compressing.
> 2) The data you're writing to the tape is already mostly
> compressed, so you won't fit as much as you might if it were
> uncompressed data.
I will do statistics about files.
> Also, the 40Gb per tape that you quote is, I think, the MAXIMUM
> amount of data the tape will take. It's only 20Gb native.
> 40Gb is how much will fit at optimum compression, which you
> never get.
> It's unlikely to be a FreeBSD problem because I regularly fit
> 6-7Gb on a DDS-2, which has a native size of 4Gb. I use dump
> options like the ones in my last message.
> --Alex
Thank, for your suggestions.
lk
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200503161350.j2GDo2fR014888>