Re: IDE DAT Drive?
On 2000-11-23 09:20, Robert Davies wrote:
>> >Can anyone offer any info about IDE DAT Backup tape drives for use under
>> >Debian? The How-tos all talk about floppy drives and I am not sure if
>> >some/all/none of these drives are supported.
>>
>> DAT isn't what I would choose to use for backups. DAT isn't known for
>> long-term reliability.
>
>Backup is about cost effective medium term storage. Long term storage is
>tricky, are you really
>sure anyone will be bothering with CD-ROM format in 30 years time? What
>about DVD? Can you even remember what peopler were using 30 years ago? I
>have over 300GB of storage to backup,
>I'm wondering how many weeks it would take just to perform one full backup
>to CD-ROM,
>no thank you!
Do you REALLY have 300G of things that need to be backed up?
If so the solution is a DLT robot. But most people who think that they have
that much data to backup aren't doing things effectively.
For example:
Don't backup *.dbb files for an LDAP directory, backup an LDIF dump (which is
25% the size).
Don't backup news spools!!!
Don't backup email as it takes too long to backup and changes too fast.
>Tape still has lowest cost per gigabyte. Earlier this year the Onstream IDE
>drives with 30GB
>capacity were the most cost effective, and having used ADR-50's from
>Onstream, they appear to
>be much more robust than DAT or DDT technology. Time will tell, the
>mechanisisms are simpler
>so there should be a lower MTBF. The IDE versions are supported by the
>kernel since 2.2.16,
>patches were available before then, and tend to be faster and more robust
>than DAT technology
>which is based on consumer audio recording. Consumer grade components are
>cheap, but tend to
>fail.
Yes.
>> Oh, don't backup user's mail directories. They change so much that a
>>backup that's more than 1 day old is probably useless.
>
>This may upset users when they loose days worth of email, that they were
>unable to download,
>or had left on the server, because they were travelling.
If you have a serious failure then users will be upset regardless. If you
use a mail server such as Netscape's mail server then due to it's databases
you would have to restore while the server is offline. Recently I was
working for a large ISP (>750K users) and I estimated that it would take 10
days to complete a backup of email. If email takes 10 days to restore then
you are better to dump it. If it takes 5 days to restore then it's probably
best dumped. How fast should a restore be to be worth-while?
I had a big discussion on this topic with my former colleagues. They
couldn't understand why backing up a mail spool (tens of millions of small
files) would be slower than backing up a web server (tens of thousands of
small files, a few really big log files, and the OS). We placed bets on the
outcome but unfortunately tape ran out before the test was 50% done so the
results weren't conclusive enough for me to be declared the winner.
>Sorry Matt, I don't know the answer about IDE DAT drives, unless you need
>DAT tape compatability
>I'd use the Onstream IDE 30GB for lowest cost. Otherwise, a reasonable SCSI
>card and drive would
>not be a bad investment, if you're worried about compatability.
I would recommend SCSI for this type of thing. Setting up tape drives is
problematic enough without going through the issues of companies that produce
low quality versions of the parts for IDE. Also compared to the cost of
tapes the cost of a SCSI controller is nothing.
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