ccwilliams@wombat.decnet.uq.oz (06/30/88)
In article <2736@tekcrl.TEK.COM>, terryl@tekcrl.TEK.COM writes: > > In article <6926@cit-vax.Caltech.Edu> mangler@cit-vax.Caltech.Edu (Don Speck) writes: > >>A 2-MIPS CPU would be inadequate to run a BSD filesystem at those speeds, >>so obviously their software overhead is a lot lower, while at the same >>time wasting no disk time. What is VM doing efficiently that Unix does >>inefficiently? > [...] > Well, it might be partially due to hardware. Remember the dedicated > I/O channels the 360-370 systems have??? Do the 4341's have anything > similar???? Similar to CDC Cyber's peripheral(sp?) processors. > [...] > mation before we can say anything. What's the layout of the file on the > disk??? What type of file is it??? Is it extent-based, or something > different. If it's extent-based, what are the sizes of the extents??? > Is there really a file system on the disk in question, or is it just that > one file???? etc..... That final point is a telling one. VM file systems are allocated in a rather primitive way. Each virtual machine/account is allocated disk in hard cylinders! yep. If you get an account on one of those machines, your disk quota will be in a multiple of one cylinder, and your cylinder will be yours forever. Unix might be a bit faster if each user had his/her own one-cylinder filesystem. It usually means there ain't nearly as much track- track seeking. Mark Williams
john@jetson.UUCP (07/12/88)
In a previous article, Mark Williams <ccwilliams@wombat.dec.net.uq.oz> writes: > Unix might be a bit faster if each user had his/her own one-cylinder > filesystem. Yes, especially without links or tree-structured directories. If you want to organize your files under VM, you get several minidisks (each an exact cylinder multiple) and put related files together.... I'll take the UNIX filesystem over that kind of speed any time. (I've worked under VM, so I know what it's like.) -- John Owens SMART HOUSE Limited Partnership john@jetson.UUCP (old uucp) uunet!jetson!john +1 301 249 6000 (internet) john%jetson.uucp@uunet.uu.net