I have always done manual forecasting with Excel. The first thing to get a
handle on is your TSM growth rate - the TSM accounting records are very
useful for this. Another problem with TSM is that every environment is so
different.
Here is a vanilla example of how you could do things:
1. Total up your onsite tape storage pools space used, total number of
onsite tapes used, and a typical max capacity number you see for your type
of media. Use these numbers to figure out what is the avg % utilized
across all tapes - 60%-70% would be typical. i.e. 10,000GB total in
onsite tape pools, using 100 LTO onsite tapes, assuming max capacity of
200GB compressed for LTO equals 50% average tape utilization.
2. Do the same thing for offsite tape storage pools - will probably be a
little less avg % utilized per tape. You'll have tapes pending and
reclamation thresholds might be higher for offsite pools.
3. Figure out your average growth rate i.e. if last month your onsite
pools were 10TB and this month they are 10.5TB, then you are growing 5% per
month. Try to trend this over as long as period as possible to get a more
accurate average growth number. I find yearly growth rates to be a little
more accurate. Will greatly depend on how far back your accounting records
go.
4. Now just take your monthly or yearly growth rate, avg tape utilization
%, and current size of storage pools and use those numbers to forecast out
x number of months. i.e. use Excel to make the calculations for you as to
how big your storage pools will be x number of months out from now. Then
just use your average tape utilization number and tape capacity to figure
out how many tapes it will take to cover that much tape storage pool space
growth. i.e. Using my sample 50% avg tape utilization number from step1,
assume that the forecast shows onsite tape storage pools to be 15,000GB 6
months from now, meaning 5,000GB in growth. That will require an
additional 50 tapes just to cover the onsite data growth. Assuming your
offsite tape utilization is a little less, then that would mean more than
50 tapes to cover the offsite tape growth that will happen also. This
doesn't count archives, backup sets, or anything else you may be doing.
Typically scratch tape counts, tapes in transit (pending status), DB backup
tapes, etc. remain fairly constant over time so I don't really factor those
in unless it is a brand new TSM customer.
5. If you do anything else special like archives, backup sets, etc. you
could also use a similar method to calculate your growth rate there as
well.
It really depends on how often people want to buy tapes as to how far you
forecast out. These estimates will also vary greatly on how accurately
your past growth rate determines your future growth rate. But I find this
to be about the closest you can get without using any 3rd party tools, and
usually gets you within 5-10% of the tape number actually needed. The most
I have ever gone out was 18 months and I have found the farther out you try
to forecast the less accurate you will be. This method should get you
really close for forecasting out 6 months at a time though. Should be good
enough to do yearly budget numbers too (if you add in a little puff).
______________________________
John Monahan
Senior Consultant Enterprise Solutions
Computech Resources, Inc.
Office: 952-833-0930 ext 109
Cell: 952-221-6938
http://www.computechresources.com
"Etchison, Jim
(SBS US)"
<james.etchison@S To
IEMENS.COM> ADSM-L AT VM.MARIST DOT EDU
Sent by: "ADSM: cc
Dist Stor
Manager" Subject
<[email protected] Tape Usage Forecasting
.EDU>
08/12/2005 02:11
PM
Please respond to
"ADSM: Dist Stor
Manager"
<[email protected]
.EDU>
Greetings,
This is my first posting to this list, so please forgive me if this is
not the right type of question or the right group to ask.
I am currently a Client Manager for a large corporation that uses TSM as
its backup solution. TSM seems to be working very well for my client,
with one glaring exception: tape usage forecasting.
On a number of occasions I have had to "surprise" my client by telling
them they needed to buy thousands of more tapes. The first few times
this has been forgiven, but with each successive request, they have
gotten more and more irritated. From what I have been told by my Storage
Manager, TSM does not have any Tape Forecasting capabilities. But from a
business standpoint, this is a very real need because it is a
substantial cost.
At this point I am left with no option but to continue suprising my
customer, which is not a career-enhancing choice. :)
My question is this: how have others resolved this dilemma? Is there an
add-on product that can be purchased that might solve this?
Any help would be welcome. Thanks!
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