LTO is a streaming data device. If you cannot keep the data flowing at tape speed, it has to stop, back up, and restart to get the tape up to speed again. This is very time-expensive in LTO because of the hardware design.
An LTO drive is 5 inches tall and roughly twice as long as the data cartridge; the motor is lightweight, and there is no tape 'buffer' between the cart and the internal reel. The motor on a 3580/3590 is much larger and heavier, and there is a vacuum column buffer between the cart and the internal reel. The net result is that the 3590 needs to get one reel or the other up to speed and has several inches of tape to accelerate AND has a much more powerful motor to do it. The LTO drive, with a lighter motor, has no tape buffer and needs to get both reels and all the tape moving. My gut feel (I haven't done 3590 in 4 years) is that LTO would be ugly in your environment because of all the small files. IBM claims to have improved the 'back-hitch' performance in the new LTO-2, but I don't think it's improved that much HTH Tom Kauffman NIBCO, Inc -----Original Message----- From: James R Owen [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 30, 2003 2:37 PM To: [EMAIL PROTECTED] Subject: ?Can LTO replace 3590E tape for busy TSM backup/restore service? ??? Do you have experience w/ or plans for replacing 3590E with LTO tapes for a busy enterprise TSM backup service? Is LTO performance OK ??? We expect to double business for one of our TSM services over next 4 years. Last year, for space and cost savings, future enhancements, etc... we bought new LTO (100GB/tape) libraries to use for Copy STGpools, replacing existing 3590E (20GB/tape) Copy STGpools which made all of those 3590E tapes available to expand our primary STGpools.) Now, we are considering whether we can use LTO tapes for new primary tape STGpools or should we continue to expand our existing 3590E tape STGpools? We have performance concerns about using LTO tapes for primary STGpools! Our current environment: ----------------------- TSM v4.2.3.2+ (upgrading to v5... soon, before 5/2003) AIX v4.3.3 (upgrading to v5... soon, before 5/2003) IBM 7025-6F1 w/ 2*600Mhz CPUs and 1GB memory IBM 3494 w/ 6 3590E drives for 1700 primary backup tapes IBM 3584 w/ 4 3580 LTO drives for 300 copy + 10 TSM DB backup tapes 2700 active clients (>100 Servers, >2500 Win*,Mac,Linux,etc. PC's) backup 5-600GB/night (some 1-4GB files, mostly much smaller files!) TSM DB: 74-76% of 120GB TSM LOG: 12GB (w/ LOGM=R needs 1 full + 1-2 incr.DB bkups daily) Our expectations for next 4 years: --------------------------------- clients: +25%/year, @+4 years = +2800 clients: +100 S, +2700 PC's backups: +25->50%/year, @+4 years = 2-4 * current backup load! how: ??? replicate another or "super-size" current TSM service? Our current LTO tape experience: ------------------------------- We use LTO tapes ONLY for an online Copy STGpool and TSM DB backups. LTO seems to be ~100% faster than 3590E tape for TSM Backup DB... LTO can be 30-50% slower than 3590E tape for TSM BAckup STGpool... w/ EMC SAN disks or 3590E tapes -> LTO vs 3590E Copy tapes. LTO can be 30-50% slower than 3590E tape for our online Copy STGpool reclaiming LTO Copy tape -> LTO Copy tape vs 3590E -> 3590E. Do you see similar or better performance? ---------------------------------------- Our concerns about replacing 3590E w/ LTO tapes for primary STGpools: -------------------------------------------------------------------- We are worried about start/stop and seeking performance using large capacity LTO tapes for restoration or reclamation of aggregated small/medium-sized files on "semi-collocated" tapes. [We use collocation, but currently have 350/1700 "filling" 3590E tapes available for 2700 clients, so we often have multiple clients' backups sharing the same 3590E tape. This problem could be much worse with 100GB LTO tapes as we might have only 70/320 "filling" LTO tapes.] Even w/ full-collocation, we believe restoration/reclamation of a highly active client's aggregated backups of many small/medium-sized files might involve substantial start/stop and seeking operations and would probably perform poorly on LTO when compared to 3590E tapes. Are our concerns warranted? -------------------------- In IBM's 2003-01-28 announcement of new Ultrium 2 LTO technology, the last paragraph under the heading "Product Positioning" states: For mission-critical data protection, optimized for enterprise multi-mode and host attachment, high-cycle and start/stop intensive tape applications, consider the proven IBM TotalStorage Enterprise Tape Drive 3590 or the IBM TotalStorage Enterprise Automated Tape Library 3494. Are TSM restores and reclamation of aggregated files start/stop intensive? Has anyone done TSM performance comparisons of LTO vs 3590E for: --------------------------------------------------------------- - DR or FS restore from (semi-collocated) tapes? - primary (semi-collocated) tape->tape reclamation? Thank you for any experienced advice you will share with us. -- [EMAIL PROTECTED] (203.432.6693)
