SCSI vs ESDI
Source Admin
src at scuzzy.uucp
Wed Jun 13 08:40:47 AEST 1990
especially on unix (or other multiuser/tasking systems scsi is a win when:
- the scsi adapter is clever (==has its own cpu, ram etc)
and is a DMA bus master that copies data by iself,
thereby offloading the main cpu a lot. also the disks
can work all at the same time.
- you have two or better more disks (and a streamer perhaps)
preferably with cache/read-ahead/request queues
- concurrent disk intensive processes run (said before)
- the organization is good.
for example my system looks like this:
/ (/dev/dsk/0s1 ): 44082 blocks 8709 i-nodes
/dos (/dev/dsk/0p1 ): 42964 blocks 65535 i-nodes
/usr (/dev/dsk/0s3 ): 83244 blocks 31665 i-nodes
/usr2 (/dev/dsk/0s4 ): 179064 blocks 54477 i-nodes
(5MB swap space on disk 0)
/tmp (/dev/dsk/1s1 ): 49166 blocks 13791 i-nodes
(15MB swap space on disk 1)
/usr/tmp (/dev/dsk/2s3 ): 3978 blocks 506 i-nodes
/usr/spool (/dev/dsk/2s4 ): 34236 blocks 34681 i-nodes
what's happening on my machine is:
- i have all binaries and nonchanging things on disk 0
- i compile everything on disk 1
- usenet news are on disk 2
- the compiler (gcc) uses /usr/tmp on disk 2
- swapping/paging uses both disk 0 and disk 1 evenly
thus disk intensive actions like compiling don't cause long seeks.
(one disk reads compiler, 'nother r/w's source, third r/w's temp files)
especially unpacking news in the background is a disk hog, so having
a disk for /usr/spool is a real win.
--
Heiko Blume blume at scuzzy.UUCP FAX (+49 30) 882 50 65
Kottbusser Damm 28 blume at netmbx.UUCP VOICE (+49 30) 691 88 93
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