kai@sp1.csrd.uiuc.edu (Kuck And Associates) (07/25/90)
I just moved our 8mm cartridge tape drive (a Megatape GT88/1) from our Alliant FX/8 to our Sequent Balance B8. On the Alliant, it was daisy chained along with a Telex 9250 to a single Xylogics 472 multibus Pertec tape drive controller. I learned that Sequent only supports a maximum of two tape drives on a 472, and they must be the same device type, sharing one tape drive formatter. We can't daisy chain the two dis-similar drives the way Alliant does, with the first drive connected as device 0 (formatter 0), and second drive as device 4 (formatter 1). With some help from tech support, I found that it is possible to put a second Xylogics 472 (we do have two) in our B8's lone multibus chassis, but then we can only use one tape drive at a time. To use both tape drives at the same time would require installing a second multibus chassis, and installing the second tape drive controller there. I have not seen this limitation mentioned in the discussion about Sequent's 8mm drive. It does explain why Sequent sells their drive with a separate controller. If Sequent's "zt" driver supported all eight drives that the 472 supports, this problem would be eliminated, and the 8mm drive would be cheaper to install. I'll report next week how monthly full backups go this coming weekend. I'll be using the plain old "dump" command that came with our Balance to write to the 8mm drive, now that it's a local device, and we'll find out if Sequent's "hdump" program really is neccessary. Patrick Wolfe (pat@kai.com, kailand!pat) System Programmer/Operations Manager, Kuck & Associates "Any opinions expressed are my own, not my employers's. Please don't call my boss and complain ... again."
kai@sp1.csrd.uiuc.edu (Kuck And Associates) (08/01/90)
kai@sp1.csrd.uiuc.edu (Kuck And Associates) writes: >I'll report next week how monthly full backups go this coming weekend. I'll be >using the plain old "dump" command that came with our Balance to write to the >8mm drive, now that it's a local device, and we'll find out if Sequent's >"hdump" program really is neccessary. The backups (using plain old "dump") went very well. I used the following options on the "dump" command: dump 0unsdbf 300000 6250 32 $DEVICE $FS Since I never try to dump more than the capacity of the tape at one time, the idea here is simply to give dump large enough numbers that it never thinks the end of tape is reached. It's always a surprise to see the time difference between running "rdump" and "dump". Dumps ran in approx 1/3 the previous "rdump" elapsed time. Tape drive throughput worked out to around 10 to 13 Mb per minute, even for the disks connected to the old "xp" Multibus disk controller. Dumps from other hosts took the same amount of time as normal. Patrick Wolfe (pat@kai.com, kailand!pat) System Programmer/Operations Manager, Kuck & Associates "Any opinions expressed are my own, not my employers's. Please don't call my boss and complain ... again."