In talking with a whole ton of people about this, this is the tentative idea:
This is for document retention, so the recovery of a whole server isn't a requirement. If I can get back a MSSQL database file, I can restore it anywhere. Same goes for a .doc or .xls file - I don't need the whole server. So my plan is to create a storage pool, call it "ARCHIVE_STGPOOL" or something. Load a bunch of scratch tapes in the 3583, run my monthly archives to that stgpool. When they're done, check them out, mark them offsite, etc. But we'd run incrementals, not monthly fulls, to keep down the db and tape usage. We're a fairly small shop (now) and only use around 3 tapes a day. I *love* that TSM is so flexible and I hate that I get to agonize and debate any changes to it for that very reason. We've been bitten really hard in the past due to poor planning, so I'm trying to plan for my next 4-7 years now. :-) -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, July 16, 2004 10:08 AM To: [EMAIL PROTECTED] Subject: Re: Thoughts on Monthly Archives ==> In article <[EMAIL PROTECTED]>, Steve Harris <[EMAIL PROTECTED]> writes: > at 1% , 1-(0.99**30), or about .25 > at 2%, 1-(0.98**30) , or about .45 > at 3%, 1-(0.97**30), or about .60 (Please feel free to correct my maths if I'm wrong - probability was never my strong point) I think your math is good; I'd add though that there's a -GREAT- deal of locality of reference: Or in other words, if 3% of your files change a day, then for user filespace probably 95% of the files that change tomorrow will be the files that chaged yesterday, and so on. I think that 25 - 30% for userdir space is probably about right. > Now, of course its often the same files which change day after day, so > real experience should be better than this, but at the time, I decided > that the overhead of mainitianing two TSMs (and two clients per node) > wasn't worth the benefit, and went with archives. But I would disagree with your logic; In place of the incremental possibilities, which would have led you at worst above to backing up 60% every month, you're choosing to back up 100% every month, without fail. I think that this represents a substantially more costly strategy. In fact, given the monthly-for-five-years figure and your numbers above, it's about twice as expensive in facilities to archive monthly than to run incrementals with similar retention characteristics; If my guess is closer to correct, it's three- to four- times the cost. For a small amount of data, this may be cheaper than the human organizational time to build two sets of nodes; but by the time you get even medium size, I think it would be pretty expensive. - Allen S. Rout
