#CD Caching slow?
3 messages in this thread
I was running a few tests on a cdrom drive under sys 7.1 with two drivers and
found some really slow times for copying 16.3 MB of ISO9660 files from CD to
HD. About 3:16 for one driver with the 4.2 apple extensions, a few seconds
less with the old driver and 3x version, and and extra 10 seconds, with another
driver. With caching enabled, it took over 5 minutes. Wonder what kind of
access is speeded up with caching, and how fast a group of files can be copied
from cd to hd. Got a transfer rate of only 85KB with the copy on a MAc II. I
expected that maybe the HD speed would give me the limit. This seems low since
I get 135KB under os/2 and 148KB under DOS with the same drive and file copy.
I knew that CD seemed slower on the mac. What kind of times do you other
owners get with big file copies. Timed from releasing the mouse after dragging
the folder to the desktop until the copy box is cleared.
A word of warning… never set a cache size of >512K. Regardless of what the
default setting may suggest, NEVER set it larger than 512K. This is true for
all versions of the Mac OS. I have documented that all SCSI performance is
severely impacted by exceptionally large cache sizes. I have seen a Quadra 950
take 20 minutes to copy a 20 meg file between two local hard disks. I believe
that their caching algorithm trashes when it has too much memory.
You can verify this yourself using a SCSI measurement program such as
Speedometer. Test after booting with different cache sizes.
-dle
Thanks on the speed checking suggestion. I plan to check further with cd.