Dwight, I agree with you on most of your analysis except for the math. 2500 * 3 minutes = 7500 min = 5+ days!
This problem of more nodes than tapes when running with collocation on is one I have been asking Tivoli to fix for a long time. A fix may be coming! See Dave Cannon's 'Scalability Enhancements' slides on the Oxford TSM Symposium web site at http://tsm-symposium.oucs.ox.ac.uk/home.html Check out the slides about 'groups'. I am not sure his presentation says this enhancement will definitely be done, so if anyone really wants it let your marketing rep know (if you can find him/her). I run with collocation on and 1,600 nodes. At any time I have only 100 - 150 filling or empty tapes so the server has to double up the nodes on each tape, actually more like 10-up to 20-up. To avoid the stress of too many mounts I only migrate down to 20% at most migration events. On weekends I migrate down to 10% and every 4th weekend after reaching 10% I switch collocation off and migrate to 0%. -- -------------------------- Bill Colwell C. S. Draper Lab Cambridge, Ma. [EMAIL PROTECTED] -------------------------- In <[EMAIL PROTECTED]>, on 11/16/01 at 10:43 AM, "Cook, Dwight E (SAIC)" <[EMAIL PROTECTED]> said: >In an event like that the normal tape selection goes like > filling tape with node's data already on it >if not then > scratch tape if "MAXSCR" for storage pool hasn't been hit AND >scratch tape still exists in the ATL >if not then > any filling tape within the storage pool >when you add a new node, it goes through the same routine when its data goes >to a tapepool... >collocation in an environment with 2500 clients will cause a bunch of tape >mounts unless you limit the maxscr's >knowing that in a 3494 ATL (with 6+ frames) you are looking at an average of >90 seconds or so for each tape mount (until it starts writing) and I'd >guess about the same for dismounts (from rewind to insert back into tape >storage slot) >so 2500 mounts/dismounts at 3 minutes each would put you at 2.08 hours for >just mounts & dismounts for migrating data from a diskpool to a tapepool and >if we are realistic, that many daily mounts would be hard on the loaders >within the tape drives... >Sure, without using collocation, eventually (from a statistic point of view) >each node would have some data on each tape and that would suck for a >restore... >as always it all depends... >I keep flip'n environments back & forth trying to do the best for the >clients and unless you have lots of clients and lots of client data and only >a small part changes nightly and only if you end up doing LOTS of complete >restores, using collocation seems to be a flip of a coin (or at least in the >environments I deal with) >Now & again we end up doing a restore of an NT box with 30 GB and that takes >a long time due to mounts/dismounts of TONS of volumes... but that might be >only once or twice a year... other than that, all our DB's are complete >archives each time so all their data that they restore is on a select few >tapes and collocation wouldn't buy anything anyway. >OK, I'm reaching the end of a page so I'll cut my reply here ;-) >later, > Dwight >-----Original Message----- >From: Luke Dahl [mailto:[EMAIL PROTECTED]] >Sent: Thursday, November 15, 2001 3:19 PM >To: [EMAIL PROTECTED] >Subject: Collocation - on or off >Hi, > We're trying to determine if we should use collocation on a system >we plan to put into production shortly. My question is whether or not >it's possible to turn collocation on and specify the number of nodes >assigned to a tape. The reason I ask is because we expect the addition >of approximately 2,500 nodes, with the majority being workstations. The >media we will be using are extended tapes holding up to 70GB >compressed. If we collocate and a individual tape is assigned to each >workstation we will waste all of that space (assuming each node will >have about 10GB aggregate over the expected subscription period) right? >Will TSM allow for shared tapes if there aren't enough tapes for each >node? What about if there aren't any scratch tapes in the library and a >new node is added? Thanks in advance! >Luke
