bernie@DIALix.oz.au (Bernd Felsche) (08/31/90)
In article <14069@cbmvax.commodore.com> jesup@cbmvax (Randell Jesup) writes: >In article <552@DIALix.UUCP> bernie@DIALix.oz.au (Bernd Felsche) writes: [..quote about AmigaDOS FS deleted..] > > Actually, it does far better at things like that than say, Unix, does. I presume that you're talking about System V.x here. Berkeley FFS does heaps better, as does SunOS, which caches block disk I/O into all available RAM. >There's been quite a bit of discussion at times in comp.arch about filesystem (I read that newsgroup as well.) >speeds, and even a 68000 amiga with a DMA controller can keep up there with >pretty high-power Unix boxes. One of the reasons is that FFS allows us to do >direct transfers to the end destination, instead of having to xfer to a buffer >pool and then cpu copy to destination (like most unix implementations). Direct transfer is a most efficient approach, and UNIX does allow this approach in limited circumstances (raw device i/o). It is used almost exculsively by high performance databases, not only for speed, but also for integrity, as UNIX 'blocking i/o' is write-delayed, and the application could never be sure if i/o was successful, and when it actually happened. > If you want to see what they can do, check out floppies under 2.0 >trackdisk and FFS. I've seen >20K/sec reads. Note that the theoretical >maximum is ~24K/sec, not including seek and settle times or any other overhead. >Trackdisk does 22K/sec via the device interface (including seek/settle) under >2.0. How about hard disks? CPU time will be a larger proportion of total time, so it will be more significant. > > Even on a 68000, sustained transfer speed is limited by disk speed >in most cases, not processor handling of the data. A 680{2,3}0 will improve >rates, but not immensely. Can you give some statistics on disk i/o for the A3000 running AmigaDOS vs A3000 running UNIX V.4? I'd prefer to compare apples (ooops) I mean Amigas with Amigas. Also, I'd be interested in how a well-worn filesystem performs; one that has quite a lot of fragmentation (>10%), for both DOS and UNIX. Which UNIX filesystem does AMIX(?) use? > > Unix FS's are faster at some things, like reading directories (assuming >the directories aren't too large - for large directories, AmigaDos is faster >at finding a file). However, FFS is no slouch at this. My directory listings >are scroll speed limited. > >>bernie >>(Real computers have flashing lights, front panel switches, 8K RAM and >>hard-sectored floppies - anybody recognize this?) > > Yes, except that's randomly-accessible tape drives, none of those >new-fangled disk things. To boot them, you have to toggle in a boot >module in octal and run it. Also, they have 12-bit words. ;-) Oh, I thought it was the one where you toggled in the boot code, and then strapped the "OS" from paper tape. Much more user-friendly. :-) bernie