nick@abblund.se (06/27/90)
Has anyone bought a rewritable optical disk from HP? Are you happy with it? We bought one a few weeks ago and use it for backup, among other things. According to HP figures on backup rates, the backup rate to an optical disk is about 900 MBytes per hour. Our experience is that it takes roughly 4 hours to back up a 300 MByte disk, i.e. 75 MBytes per hour. We have asked HP about this several times, but nobody seemed to know anything. We use cpio to do backups, exactly as recommended in the manual. Are we doing anything wrong? Does anyone else have similar or different experiences? -- Nick Hoggard ABB Corporate Research, Lund, Sweden nick@abblund.se or ...mcvax!enea!abblund!nick
bill@iccdev.indcomp.com (Bill Gaines) (06/28/90)
nick@abblund.se writes: >Has anyone bought a rewritable optical disk from HP? Are >you happy with it? >We bought one a few weeks ago and use it for backup, among other >things. According to HP figures on backup rates, the backup rate >to an optical disk is about 900 MBytes per hour. Our experience >is that it takes roughly 4 hours to back up a 300 MByte disk, >i.e. 75 MBytes per hour. We have asked HP about this several times, >but nobody seemed to know anything. We use cpio to do backups, exactly >as recommended in the manual. Are we doing anything wrong? Does >anyone else have similar or different experiences? We noticed the same thing about ours. However, when we finally looked in the back of the manual for the drive we found that it writes 4 times slower than it reads. We have noticed that reading information is very acceptable on this drive, but writing is very slow. -- Bill Gaines Industrial Computer Corp. bill@iccdev.indcomp.com (...!gatech!iccdev!bill)
nick@bischeops.UUCP (Nick Bender) (06/28/90)
In article <1990Jun27.071237.7621@abblund.se>, nick@abblund.se writes: > > Has anyone bought a rewritable optical disk from HP? Are > you happy with it? > > We bought one a few weeks ago and use it for backup, among other > things. According to HP figures on backup rates, the backup rate > to an optical disk is about 900 MBytes per hour. Our experience > is that it takes roughly 4 hours to back up a 300 MByte disk, > i.e. 75 MBytes per hour. We have asked HP about this several times, > but nobody seemed to know anything. We use cpio to do backups, exactly > as recommended in the manual. Are we doing anything wrong? Does > anyone else have similar or different experiences? > -- > Nick Hoggard > ABB Corporate Research, Lund, Sweden > nick@abblund.se or ...mcvax!enea!abblund!nick We have one and have been using it for backups over a network. Using dump it takes about 90 minutes to backup a 300 meg drive with 200 meg in use with the following command: dump 0uf - /filesystem | compress -c | remsh otherHost "cat > dumpfile" This ends up writing around 120 meg on the optical so *if* the backup is limited by the write time on the disk then it's transfering at 80 meg per hour, but it only has to write half as much data. Presumably you could do the same type of thing by piping cpio's output through compress. Of course the backup is doing other things so you may not be bound by the optical speed. In fact, # ls -l /hp-ux -rwxr-xr-x 1 root sys 1076540 Mar 17 16:10 /hp-ux* # time cat /hp-ux /hp-ux /hp-ux /hp-ux /hp-xu > /optical/junk 0.1u 4.1s 1:03 6% So cat delivers roughly 300 meg/hour - this would indicate that the backup procedure itself is fairly costly. Oh yeah, all this on a 9000/370. Maybe HP is talking about raw disk-to-disk transfer on a screaming 800 machine... Nick Bender Lempel-Ziv Fan Club