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Guest
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 Posted:
Fri Sep 23, 2005 2:18 pm Post subject:
how to calculate tape-capacity ? |
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Hello,
are there some guidelines available how to calculate
the capacity of a tape drive?
(I understand that a large tape-capacity means fewer tape
changes, lower administrative overhead, and fewer operator errors)
Any tip is appreciated very much. Thank you!
John |
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Anton Rang
Guest
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| Posted:
Fri Sep 23, 2005 4:16 pm Post subject:
Re: how to calculate tape-capacity ? |
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hardware55@bluemail.ch writes:
| Quote: | are there some guidelines available how to calculate
the capacity of a tape drive?
|
Ummmm, what question are you trying to answer?
Here are two answers:
(1) The capacity of a tape drive is one tape, but if you add an autoloader,
it can hold more than one tape. A tape library has a bigger capacity,
and you can read its capacity from the data book.
(2) Tape drives don't have a capacity, but tapes do. You can read the
capacity from the box. If you know how well your data compresses,
you can calculate how much of it will fit based on the uncompressed
capacity. If you don't, then assume (unless you have a lot of text or
database files) that the data will compress very little, and use the
uncompressed capacity as a guideline.
| Quote: | (I understand that a large tape-capacity means fewer tape
changes, lower administrative overhead, and fewer operator errors)
|
Also means slower random access to data and more expensive tapes.
What problem are you trying to solve? You should figure out how much
data you will be backing up (depends on your backup schedule, too),
how long you can tolerate for the backup to take, and then probably
work with a consultant (unless you're willing to take more time to
educate yourself) on selecting backup software, servers, and tape
drives and/or libraries.
(Or, if you're not looking at backup but at HSM or something similar,
define your problem needs; it's even more complex in that case, as you
would probably want a mix of different tape types for capacity vs. speed.)
Anton |
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Joe Bloggs
Guest
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| Posted:
Sun Sep 25, 2005 4:15 pm Post subject:
Re: how to calculate tape-capacity ? |
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<hardware55@bluemail.ch> wrote in message
news:1127467109.020530.273430@g44g2000cwa.googlegroups.com...
| Quote: | Hello,
are there some guidelines available how to calculate
the capacity of a tape drive?
(I understand that a large tape-capacity means fewer tape
changes, lower administrative overhead, and fewer operator errors)
Any tip is appreciated very much. Thank you!
John
|
Each tape drive technology has its own typical capacities. Eg, LTO=average
of 200MB, LTO2=average of 400MB.
Which tape drive did you want to know about John, and writing what sort of
data to it (database, file server etc) |
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Guest
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| Posted:
Thu Sep 29, 2005 2:31 pm Post subject:
Re: how to calculate tape-capacity ? |
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Joe Bloggs wrote:
| Quote: | hardware55@bluemail.ch> wrote in message
news:1127467109.020530.273430@g44g2000cwa.googlegroups.com...
Hello,
are there some guidelines available how to calculate
the capacity of a tape drive?
(I understand that a large tape-capacity means fewer tape
changes, lower administrative overhead, and fewer operator errors)
Any tip is appreciated very much. Thank you!
John
Each tape drive technology has its own typical capacities. Eg, LTO=average
of 200MB, LTO2=average of 400MB.
Which tape drive did you want to know about John, and writing what sort of
data to it (database, file server etc)
|
Only about 1 GB database files and 1 GB file server.
DDS/5 would probably be sufficient, but in the past
we dint`t made only good experiences with those kind of
drives..
So I am tempted to opt for LTO2. But with LTO2, I
expect that we would try to save costs for the media/
tapes and use (too)few tapes. Therefore if one of the
LTO2-tapes would fail or gets lost, the problem would
probably be even worser...
Thank`s a lot for for any feedback!
John |
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RPR
Guest
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| Posted:
Sat Oct 08, 2005 11:34 pm Post subject:
Re: how to calculate tape-capacity ? |
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I don't know if tape is cost effective these days for 1 or 2 GB. You'll
have to run many, many backups to amortize the cost of the drive.
You'll have to write many backups to each tape, which reduces
reliability because you're handling each tape many times (or leave it
in the drive for extended periods of time), and if a tape fails you
lose many backups as you said. A loader is definitely overkill.
DVD or even CD based backup might be more appropriate, unless you need
long term (>10 years) archiving or expect your data volume to grow
dramatically soon.
Ralf-Peter |
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