That's a great beginning to figuring out how many tapes you will need. If your
backup/archive schedules have not changed for a month... suggest doing:
q actl begindate=-30 search=ANR1214
Take the amount of data copied from your primary tapepool to copy tapepool for
each day and add it up and divide by
30 for both backups and archives. Then divide this amount of data by the average
for all storage pools as computed by
Wanda's SQL... this should be as accurate as any way of determining the amount
of tapes required and then you should
plus this amount up by suspected or anticipated growth. You could do this on a
yearly basis to determine what the average
growth rate of what is being backed up is and intelligently guess how many tapes
to purchase (or how long it will take the
developers to finish a software project ;-) George
"Prather, Wanda" <[EMAIL PROTECTED]> on 02/16/2001 02:01:11 PM
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cc: (bcc: George Lesho/Partners/AFC)
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Subject: Re: Formula to calculate # tapes required
I agree. Here is a query that will do it for you:
select stgpool_name as stgpool,
cast(mean(est_capacity_MB/1024) as decimal(5,2)) as
gb_per_FULL_vol from volumes where status='FULL' group by
stgpool_name
-----Original Message-----
From: George Lesho [mailto:[EMAIL PROTECTED]]
Sent: Friday, February 16, 2001 2:26 PM
To: [EMAIL PROTECTED]
Subject: Re: Formula to calculate # tapes required
The effect of compression is not linear if you are compressing various types
of
data. To illustrate:
00E3A9 BKTPOOL1 3575DEVC1 36,598.5
100.0 Full
00E390 BKTPOOL1 3575DEVC1 6,794.6
100.0 Full
Both volumes are Magstar MP C-FOrmat XL 7gb tapes. I would recommend summing
the
"full" volumes and dividing by the
number summed to get an average full volume value which will reflect the
various
data types being compressed. I am
using compression at the drive and not the client.
George Lesho
Storage/System Admin
AFC Enterprises
Paul Zarnowski <[EMAIL PROTECTED]> on 02/15/2001 05:36:34 PM
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Subject: Re: Formula to calculate # tapes required
At 04:50 PM 2/15/2001 -0500, Prather, Wanda wrote:
>The formula I use is:
>
>Need to back up xxx TB
>Divid by the number of GB that will fit on a tape.
>Adjust as you have suggested for extra versions
>Divide by .65 on the assumption that the not-yet-reclaimed tapes will be,
on
>average, 65% full
>Multiply by 2 for the offsite copies
This is pretty close to what I use, too, but make sure you factor in
compression somewhere. Also, if you are using collocation, then you also
need to consider how rapidly your data is changing. If you have high data
turnover, then you will be reclaiming data more frequently. If you don't
have enough tape drives or wall clock time to handle this, you will need
more tapes, plan on a lower average tape utilization, and raise your
reclaim threshold to relieve the pressure on reclaim.
This reclaim issue will not surface at first in a new robot. You will only
run into it over time, after a bunch of your tapes have filled up and you
start doing more reclaims. This issue is also dependent on the tape
technology you are using, as some perform reclaims faster than others.
..Paul
