Mark, I fully agree with your opinion. TSM *can* work with single drive but it would be ugly. Same waste of resources as assignment to 5k project a project manager with 300k salary (and you can always send 1 kg parcel with a truck). I said it is possible but will never say I recommend it.
Zlatko Krastev IT Consultant Please respond to "ADSM: Dist Stor Manager" <[EMAIL PROTECTED]> Sent by: "ADSM: Dist Stor Manager" <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] cc: Subject: Re: 2 drives are required for LTO? From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED]]On Behalf Of Zlatko Krastev > The requirement for 2 drives is not mandatory, it ought to be just a > suggestion. LTO can be used as a standalone drive, TSM can use single > drive or small autoloader with single drive. So it is NOT required but > recommended. Yes, technically a single drive is sufficient to do backups. But then I could use a pair of nail scissors to mow my lawn... > - single drive reclamation - define reclamation storage pool of type FILE. > On reclamation remaining data is moved to files and later written to new > tape volume. Drawback: data is not read when written (sequential > read+write vs. parallel) thus takes more time. Calculate time budget > around the clock. FILE storage pool-based reclamation is dog slow, and expensive of disk space, particularly if you are backing up database-type data of any size. I've got a customer trying to do this very thing, and reclamation is extremely slow. > - single drive copypools - define following hierarchy DISK -> FILE -> LTO > (file pool would be also lto reclamation pool). Prevent file->lto > migration during backups (highmig=100). Perform backups to copypool after > node backups finish. Allow migration after backup to copypool finishes. > Drawbacks: filepool must be large enough to hold all backups data. Backups > should not happen during migration because some object(s) may migrate > without being copied to the copypool. Again time - data have to be written > twice through the one-and-only drive. And on the end with one drive there > is no way to perform copypool reclamation. Bingo. A single tape drive, because of the lack of reclamation, means no usable copy pool, no way to use move data to consolidate primary tape volumes, and no way to use a restore volume command to rebuild bad primary pool media from copy pool media--in short, a badly crippled TSM backup system. > Conclusion: for a small installation data might be not too much, time > might be enough for all activities (node backups, copypool backup, primary > pool raclamation, migration, DB backup). Thus neither LTO technology nor > TSM dictate number of drives to be used but only the business requirements > you have. Don't let anyone tell you that a single tape drive is adequate for anything resembling a real backup system. If you can't afford a real library, you can't afford a real backup system. My experience with multiple environments calls for a minimum of three drives--two drives for multitape operations, and a spare in case one drive breaks down. -- Mark Stapleton ([EMAIL PROTECTED]) Certified TSM consultant Certified AIX system engineer MCSE