Re: Informix database backups

In article <1992Apr29.052048.18203@anasaz> Chad R. Larson wrote: >In article <181269@pyramid.pyramid.com> echen@sword.eng.pyramid.com >(Eric Chen) writes: >+--------------- >| The advantages of using tbtape command are: >| >| * On-line backup and databases are not locked. A must for commerical >| environment. >+--------------- >Not exactly. The database gets locked if the archive doesn't fit on >a single reel. The lock exists during the time the tape is rewinding >and the operator is mounting a new reel. This can be several minutes, >and is completely unacceptable. I agree with you. >We had to solve this problem for our commercial customers. Our approach >was to create a named pipe (/dev/tape) and point Informix at it in the >tbconfig file. We lied to Informix about the size of the tape device >(99999999...) and then wrote our own set of programs to read the pipe >and write the tape. Our programs can toggle drives on systems that >have more than one, and buffer to disk during the time the tape is >not available. > If the tape device is designed like RAID to provide "concate/stripe virtual tape" by spreading output to several(configurable) tape device in transparent way, then it will eliminate not only the problem you mentioned above but also tape channel performance bottleneck ! Does this product exist? Yes !! But how about the other performance bottleneck -- the single thread I/O as done by tbtape to read data off the disk is still there. Did you guys provide any solution on that for customers ? The typical speed of reading database off disk is probably 600 - 800 KB/s which means 20 hours to do 50GB database and I doubt the "commercial customers" still care the few minutes locking between changing tape reels :-) Your response is welcomed. ========================================================================== Eric Chen Database Division, Pyramid Technology echen@pyramid.com ==========================================================================