chukran@austin.iinus1.ibm.com (04/22/91)
Can anyone confirm that writing floppys are very inefficient and that there might be a workaround or fix? I observe that reading a 3.5" floppy using dd takes 50s using a block size of 1 track (18*512) from device /dev/rfva0, which is as I would expect. However writing the same device takes 610s using the same block size. I varied the device as rfva0 and fva0, and varied the block size from 512, 3*512, 9*512, and 18*512, and still get the same real time measure. Its as if the device driver is writing to the device one block at a time. dd if=/tmp/floppyimage ibs=9216 obs=9216 of=/dev/rfva0 Kind of makes making floppy backups tedious. Rudy Chukran
marke@richs118.cpg.trs.reuter.com (Mark Ellis) (04/23/91)
Thought this sounded interesting, so as an experiment, I wrote this dumb shell script: date dd if=/dev/rfd0 of=/tmp/tmp date and ran in on a Sun Sparc1+ with a 3.5" HD floppy. It took 6 sec. short of 10 minutes to READ the entire floppy. The resulting output file (/tmp/tmp) was 1474560 bytes. Hope this helps. (P.S. Running Sun-OS 4.1)