DAT Autochangers (6/24gb)

Is it just me or are these things fundamentally flawed?? I've got a 12/24gb
6-Tape Autoloader which will store up to 144gb (72gb uncompressed - 12gb * 6
tapes).

To actually backup that amount of data, considering the speed of the DDS-3
drive, would take about 24 hours. Does anybody actually do this?

Please see cross-post and follow-up to comp.periphs.scsi
You might get more responses there. :-)

Carl Farrington <(E-Mail Removed)> wrote:

> Is it just me or are these things fundamentally flawed?? I've got a
> 12/24gb 6-Tape Autoloader which will store up to 144gb (72gb uncompressed
> - 12gb * 6 tapes).
>
> To actually backup that amount of data, considering the speed of the
> DDS-3 drive, would take about 24 hours. Does anybody actually do this?

I have no tape-library but only a single DDS3 drive. It is
right it takes quite some time to backup an amount of 12 GB
data. My tape runs with 920KBps using DDS3 tapes, and 600KBps
using DDS2 tapes.

You could speed up the backup time if you use compression.
However the speed-up depends on the compression ratio and
it is only advisable to compress file by file and not the
entire archive as a whole.

I have no problem with this speed because I use it to backup
data from my private PC which does not run around the clock,
so there is much time left for backing up. However I've to
admit that I was shocked first when I bought the tape drive
and detected that it would take 4 hours to backup 12 GB.


Ciao, Horst
--
»When pings go wrong (It hurts me too)« E.Clapton/E.James/P.Tscharn

Carl Farrington <(E-Mail Removed)> wrote:
> Is it just me or are these things fundamentally flawed?? I've got a 12/24gb
> 6-Tape Autoloader which will store up to 144gb (72gb uncompressed - 12gb * 6
> tapes).

> To actually backup that amount of data, considering the speed of the DDS-3
> drive, would take about 24 hours. Does anybody actually do this?

What's the problem? If you need more speed you should consider a few fast
DLT tapes and some backup sw capable of writing multiple streams at once
to different tapes, you are likely in need of gigabit NICs for this.


--
Michael Heiming

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"Carl Farrington" <(E-Mail Removed)> said:
>Is it just me or are these things fundamentally flawed?? I've got a 12/24gb
>6-Tape Autoloader which will store up to 144gb (72gb uncompressed - 12gb * 6
>tapes).
>
>To actually backup that amount of data, considering the speed of the DDS-3
>drive, would take about 24 hours. Does anybody actually do this?

That's not the only way to use those things.

F.ex. consider a situation where a single backup set fits on a single tape.
Have 5 data tapes and a cleaning tape loaded to the changer. This makes it
so that all data on some single tape comes from a certain day. The changer
gives you the possibility to have one weeks worth of backups online - and
still have room for the cleaning tape. Depending on the system, your
maintenance duty could then be that once a month you pick up a single tape
to some offsite storage (and of course place a fresh tape into the changer)
and rest of the time the backup can run unattended. As long as the changer
and/or tapes are not harmed, you can restore any file to any situation
within the last five weeks. If it so happens that your primary data (machine)
is lost along with the tapes in the changer, you still can most probably
restore the situation to the latest "1-month" tape you had taken offsite.

Another possible rotation scheme could be to load a full 6-tape pack in
the changed on Friday before leaving the office, letting the backup system
make an automated full backup during the weekend. Then on Monday morning
switch to another cartridge to which you take backup of the changed files
during the week (Mon-Thu).
--
Wolf a.k.a. Juha Laiho Espoo, Finland
(GC 3.0) GIT d- s+: a C++ ULSH++++$ P++@ L+++ E- W+$@ N++ !K w !O !M V
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Carl Farrington <(E-Mail Removed)> wrote:
> Is it just me or are these things fundamentally flawed?? I've got a 12/24gb
> 6-Tape Autoloader which will store up to 144gb (72gb uncompressed - 12gb * 6
> tapes).

> To actually backup that amount of data, considering the speed of the DDS-3
> drive, would take about 24 hours. Does anybody actually do this?

Juha pointed out how they are intended to be used a few posts down.

Despite that, I still despise these things.

I find the autochangers and the tapes themselves to be
unreliable. Not only that, but the tapes, once written don't have a
very good shelf life. I find that you can't reuse them many times
either, at least if you consider your data important.

If you can afford them, I suggest DLT (getting a bit obsolete, and get
at least DLT IV) or LTO tapes and libraries. Vastly more reliable,
vastly more capacity, and a lot faster as well.

Unless you get a good deal on a used one, a bit out of the price of a
home user though. I'm staying away from used ones for home use too, as
repair/replacement costs once you get to depend on them are pretty
high...

You'd drool over the several 100+ slot DLT and LTO libraries I've got
at work... :-)

--
Jim Buchanan (E-Mail Removed)
=================== http://www.buchanan1.net/ ==========================
"There is a general social trend in English-speaking countries to
treat technically-educated people as the social inferiors of
non-technically educated people. This is a terrible ill affecting our
society" -Bruce Perens
================= Visit: http://www.thehungersite.com ==================

Juha Laiho wrote:
> "Carl Farrington" <(E-Mail Removed)> said:
>> Is it just me or are these things fundamentally flawed?? I've got a
>> 12/24gb 6-Tape Autoloader which will store up to 144gb (72gb
>> uncompressed - 12gb * 6 tapes).
>>
>> To actually backup that amount of data, considering the speed of the
>> DDS-3 drive, would take about 24 hours. Does anybody actually do
>> this?
>
> That's not the only way to use those things.
>
> F.ex. consider a situation where a single backup set fits on a single
> tape. Have 5 data tapes and a cleaning tape loaded to the changer.
> This makes it so that all data on some single tape comes from a
> certain day. The changer gives you the possibility to have one weeks
> worth of backups online - and still have room for the cleaning tape.
> Depending on the system, your maintenance duty could then be that
> once a month you pick up a single tape to some offsite storage (and
> of course place a fresh tape into the changer) and rest of the time
> the backup can run unattended. As long as the changer and/or tapes
> are not harmed, you can restore any file to any situation within the
> last five weeks. If it so happens that your primary data (machine) is
> lost along with the tapes in the changer, you still can most probably
> restore the situation to the latest "1-month" tape you had taken
> offsite.
>

Thank you Juha! This explains perfectly why when I bought the device (used),
it came with 5 data tapes & 1 cleaning tape in the magazine! It also
describes a very useful situation which had not occured to me.

Thank you.

(E-Mail Removed) wrote:
> Carl Farrington <(E-Mail Removed)> wrote:
>> Is it just me or are these things fundamentally flawed?? I've got a
>> 12/24gb 6-Tape Autoloader which will store up to 144gb (72gb
>> uncompressed - 12gb * 6 tapes).
>
>> To actually backup that amount of data, considering the speed of the
>> DDS-3 drive, would take about 24 hours. Does anybody actually do
>> this?
>
> Juha pointed out how they are intended to be used a few posts down.
>
> Despite that, I still despise these things.
>
> I find the autochangers and the tapes themselves to be
> unreliable. Not only that, but the tapes, once written don't have a
> very good shelf life. I find that you can't reuse them many times
> either, at least if you consider your data important.
>
> If you can afford them, I suggest DLT (getting a bit obsolete, and get
> at least DLT IV) or LTO tapes and libraries. Vastly more reliable,
> vastly more capacity, and a lot faster as well.
>

I did just buy a DLT7000 with Adaptec 2940u2w for £169. Not a bad deal eh?
Sold it to a client though. I do like DLT IV - 5Mb/sec is pretty nice.
What's really nuts though is Ultrium 2 (LTO 2) - 60Mb/sec - that's 3.6Gb /
min!!! wooooooooo!

I've put the Autochanger on eBay because it's not going to be any use to my
clients, nor me. I really need to read a good guide on Backup strategies. At
the moment I have everybody doing Full backups every night onto a different
tape (1 for each day of the week). Could never understand the reason for
incremental backups, but now I think it must drastically increase the
lifetime of both tape & drive (speaking in terms of DDS4 / DDS3 DAT here).
But since I've only 'thought' about this, and it never occured to me how the
Autochanger should be used, I definately think I need to read a book.
After I've read one on Kerberos, then ldap.... there I was wanting to learn
to speak Italian but I have all this stuff I don't know enough about
already!

cheers!

Carl Farrington <(E-Mail Removed)> wrote:
> tape (1 for each day of the week). Could never understand the reason for
> incremental backups, but now I think it must drastically increase the

Network bandwidth.

We back up around 11TB of data, distributed around a large campus,
we'd never be able to do a full on all of it every night, there just
isn't enough bandwidth. (Plus we'd spend a lot more more on tapes, we
keep backups one year)

So we do 1/7 of the fulls every night and 6/7 of the data gets
incremental backups. It can still be touch and go as to whether we
make the backup window.

I'm glad I'm the secondary backup guy now, I was primary for some
years, but now that Linux is taking of, I've moved to that full
time. Much lower tension level.

--
Jim Buchanan (E-Mail Removed)
=================== http://www.buchanan1.net/ ==========================
"Nothing is real but the way that I feel, and I feel like going down,
down, down..." -Ronnie James Dio
================= Visit: http://www.thehungersite.com ==================

Carl Farrington <(E-Mail Removed)> wrote:

....

> But since I've only 'thought' about this, and it never occured to me how the
> Autochanger should be used, I definately think I need to read a book.

Get "Unix Backup & Recovery" from O'Reilly, great book.


--
Michael Heiming

Remove +SIGNS and www. if you expect an answer, sorry for
inconvenience, but I get tons of SPAM