RE: TAPE BLOCK SIZE
Darin - Sounds like an older version of OnLine. In (I believe) the early 5.0 days (maybe 4.x), tbtape read through EVERY page, used or not, as part of the archive process. In some later versions (still 5.x), tbtape reads the chunk free list. If an extent is allocated, but not used, tbtape may still be reading the pages. This by itself will account for some of the extra time to complete the archive. Are you using the extended length tapes with your 8505 ?? Are you using h/w compression ?? The way 8505's get 14-15GB per tape, is through compression and extended length tapes. Remember, the way they get the extended length, is the same way they did it with audio tapes, by making the tape thinner....just a word of caution. Using h/w compression, in my tests, has improved the time to complete archives, significantly. However, Informix's position has been, that they do not recommend or support the use of h/w compression. Jon ------------------------------ Jon C. Vemo jvemo@cyberspace.com Bothell, WA U.S.A. ---------- From: Darin Melin[SMTP:melin@bsi.sps.mot.com] Sent: Monday, March 18, 1996 11:41 PM To: Cheryl Kendricks Cc: Informix List on WWW Subject: Re: TAPE BLOCK SIZE On Mon, 18 Mar 1996, Cheryl Kendricks wrote: > I am running tbtape from UNIX 3.2 and Informix 5.X engine on IBM RS6000. I > have a 10GB database and am using 5.0 GB IBM 8MM Tape Drive. It takes 4 hours > to do a back up. We are using a blocking of 20 in the Informix Configuration > and the tape block size is set to 20480. I have changed this to 240 for the > Informix Configuration and 245760 for the tape drive. I then got a to 3 hours. > So smart me changed it to 960 hoping it would at least get to 2 hours, if not > one. BUT NO It went back to 4 and used more tapes. > > Anyway my question is does anyone know a MAGICAL set of tape drive and > configuration numbers that I could try to get this archive to process in > at least 2 hours? > > If you do please let me know. I and the operators would love it if we could > cut our archive down to 1/2 the time. > > THANKS IN ADVANCE!!!!!!!!!!!!!!!!!!!!!!! > ------------------------------------------------------------------------- > Cheryl Kendricks > Internet: cherylk@spamis.jcdc.doleta.gov > OR > cherylk@prod1.jcdc.doleta.gov > OR > kendric@gwysmtp.jcdc.doleta.gov > DTSI, Inc. Voice: 1-800-598-5008 > Database Administrator - DOL Job Corps San Marcos, Texas > ------------------------------------------------------------------------ Cheryl, I am also having the same problem. My configuration is a Sparcenter 2000 with Exabyte 8505 8mm tape drives. These drives allow 14 GB to be written to them. I have tried different device numbers and can't write more than 8GB to them. In addition, my database is 40GB allocated and it takes me 24 hours to back it up (ie 3 tapes at 8 GB each) (no my math is not wrong, we are not full on the dbspaces). When I do a restore, it takes approx 2 hours per tape. Anybody know the discrepancy??? I am the only one on the system during archive and restore. Also, Anybody know the proper settings for block factor, etc? Thanks, Darin +----------------------------------------------------------------------- -----+ | | | | . . | | | ... ... | Darin Melin | | ..... ..... | Software Engineer, DBA | | .. ... .. | Business Systems Integration Group | | . . . | Semiconductor Products Sector - LATG | | | 2100 E. Elliot Road, MD EL557 | | | Tempe, AZ 85284 | | Motorola, Inc. | rp29560@email.sps.mot.com Phone:(602) 413-5756 | | | melin@bsi.sps.mot.com FAX: (602) 413-5566 | | | Director - Arizona Informix Users Group | +----------------------------------------------------------------------- -----+ | 'connectionLESS IS MORE' -- Data Broker | +----------------------------------------------------------------------- -----+