ridder@elvira.enet.dec.com (Hans Ridder) (06/09/91)
I got the new V6.6 A2091 ROMs a few weeks ago, and finally had a chance to try doing a backup to tape. I don't know what I could be doing wrong, but the backup performance is worse than ever. And yes, I did re-enable reselect, first using the "ReselectOn" program, and then with the HDToolbox. Randell Jesup's "readrdsk" program even says reselect is enabled. Here's the whole story. I have a 3 meg. A2000HD running 1.3, a 3M MCD-40 tape drive, and am using BTNtape and tar for backups. Using the old ROMs, with reselect enabled, the tape drive would keep streaming most of the time. The only time it stopped and backed up was when there were lots of small files in a row. This worked fine most of the time, but it was fairly scary to do a restore with reselect enabled. (The system would hang, leaving the hard disk corrupt.) Turning off reselect caused the tape drive to stop more often, almost doubling the backup time. Now, with the new ROMs, the disk drive access "feels" like reselect is enabled. But when doing a backup, the tape drive stops and backs up after *each* block (larger block sizes just make it go longer between stops, I could use alot of memory for buffers to get back the old performance.) I haven't completed a backup yet, but at this rate it should be about 5-10 times slower than with the old ROM's and reselect enabled. From what I can tell, the new ROMs aren't using reselect to the tape drive, where the old ROMs did. This is just a guess at this point. I tried the V2.0 BTNtape, but no difference. The real bugger is that my old ROMs were already sent back to Commodore.... Any ideas? Any help? Randell, anyone? -hans ------------------------------------------------------------------------ Hans-Gabriel Ridder Digital Equipment Corporation ridder@elvira.enet.dec.com Customer Support Center ...decwrl!elvira.enet!ridder Colorado Springs, CO
ridder@elvira.enet.dec.com (Hans Ridder) (06/20/91)
In article <3325@shodha.enet.dec.com> ridder@elvira.enet.dec.com (Hans Ridder) writes: >I got the new V6.6 A2091 ROMs a few weeks ago, and finally had a chance >to try doing a backup to tape. I don't know what I could be doing >wrong, but the backup performance is worse than ever. > >Here's the whole story. I have a 3 meg. A2000HD running 1.3, a 3M >MCD-40 tape drive, and am using BTNtape and tar for backups. After all the noise about the reselect problems on the A2091, I would have thought I'd get more response to my posting.... (Maybe everyone knew I'm nuts, huh?) For the record, the V6.6 A2091 roms are just fine. They reselected their way through about a dozen backups without a hitch. The problem was (mostly) pilot error. For the benefit of other 3M MCD-40 owners and BTNtape users, when I formatted some new tapes to do the backups on, I used the 2.0 version of BTNtape. It suggestes a format command which specifies an interleave of two, while the 1.0 version has a file specifying an interleave of three. I didn't notice the difference. The lower interleave factor means that the average data rate is higher, and the disk couldn't keep up with the tape causing the tape to stop. After some messing around with the tapes interleaved at two, I found that by upping the handler priority to 11 (higher than the disk file system) and upping the blocking factor ("NB" parameter) to 4, I can backup 37 meg of data in 34 minutes. (It used to take about 30 minutes for 10 meg.) The net result is a faster backup than ever! Increasing the blocking factor to 10 reduces the time to 32 minutes (and only about 160 Kbytes of buffer space is used :-)) Just for reference, with the increased priority and block size, the tapes with an interleave of three give a backup time of 49 minutes. >-hans -hans (again) ------------------------------------------------------------------------ Hans-Gabriel Ridder Digital Equipment Corporation ridder@elvira.enet.dec.com Customer Support Center ...decwrl!elvira.enet!ridder Colorado Springs, CO