VanLUG Email Archive
> So the question comes up: what interface should the main disk(s) use?
> Is SCSI still sufficiently better than EIDE to justify the extra price
> of the drives?
For any typical drive size, the manufacturers will make a few different
drive models with different levels of performance. The cheap line is
usually EIDE only and slow, the middle line available in both EIDE and
SCSI (and pretty much the same speed either way), and the top-notch drives
are SCSI only. Unless you're buying the fastest drive models, EIDE is
usually fine.
> Do UDMA drives actually get decent transfer rates, comparable to SCSI,
> these days?
Current EIDE UDMA drives are much faster than the fastest SCSI drives of
only a couple years ago, but they're not the fastest drives on the market.
SCSI used to have a huge advantage in CPU utilization over IDE, but the
newer UDMA drives combined with a good EIDE adapter (TX or VX chipset for
Socket 7 or any of the Slot 1 chipsets) have gotten pretty close. I
personally don't think there's anything wrong with EIDE on a big
workstation, but a serious server is still probably best served by SCSI.
At the very least, you're not limited to four devices with SCSI.
> Is it actually better to have the disk on an EIDE controller to balance
> load between it and the SCSI controller?
If any of your SCSI devices hog the bus, perhaps by not supporting
disconnect or running at a slow async rate, then it would probably help a
great deal. But then a 2nd SCSI bus would too. I'd be concerned about
the scanner's bus manners at the very least.
Note that UDMA isn't much advantage in Win 9x, as DOS 7 still busywaits on
I/O. Linux takes advantage of it. No idea whether NT can.
> Is there any problem booting Windows or Linux on a SCSI-only system with
> no EIDE disk?
None I know of, except perhaps keeping your kernels near the front of
the disk.
> How about mixed EIDE and SCSI - can you boot from either?
Depends on your motherboard BIOS. If your mb SCSI BIOS or SCSI adapter
BIOS is available at boot, you can put LILO on the EIDE drive and the
kernel/root fs on a SCSI partition. Better yet, your BIOS may let you
choose what device to boot from.
> A similar question for the CD-ROM (assume it's internal): should it be
> EIDE/ATAPI (cheap) or SCSI?
I don't think there's any real problem with ATAPI CD-ROM drives, but I'd
definitely go SCSI for a burner.
My own system consists of two EIDE UDMA drives and a 24x ATAPI CDROM, and
a NCR 53C810 SCSI controller with an old 2G drive, 4x CDROM and 2x CD
burner. I boot from EIDE for both 98 and Linux.
Here's some numbers in case anyone is interested. Auggy is a P225 MMX
(75x3) on a TX97 w/128MB of SDRAM, kernel 2.0.35, no swap configured,
XFree w/Netscape and a bunch of nxterms open, and me tapping away in a
couple of ssh sessions. /u is an almost fresh ext2 filesystem on hdc1.
---
root@auggy:/home/tom# ./bonnie -d /u/tmp -s 256 -m auggy
File '/u/tmp/bonnie.689', size: 268435456
Writing with putc()...done
Rewriting...done
Writing intelligently...done
Reading with getc()...done
Reading intelligently...done
Seeker 1...Seeker 3...Seeker 2...start 'em...done...done...done...
-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
auggy 256 2693 93.8 9315 48.0 3725 33.8 3003 95.7 11319 36.1 62.8 1.9
root@auggy:/home/tom# hdparm -it /dev/hdc
Model=QUANTUM FIREBALL EL7.6A, FwRev=A08.1100, SerialNo=34781633
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
RawCHS=15907/15/63, TrkSize=32256, SectSize=21298, ECCbytes=4
BuffType=3(DualPortCache), BuffSize=418kB, MaxMultSect=16, MultSect=8
DblWordIO=no, maxPIO=2(fast), DMA=yes, maxDMA=2(fast)
CurCHS=15907/15/63, CurSects=15032115, LBA=yes, LBAsects=15032115
tDMA={min:120,rec:120}, DMA modes: sword0 sword1 sword2 mword0 mword1 mword2
IORDY=on/off, tPIO={min:120,w/IORDY:120}, PIO modes: mode3 mode4
Timing buffered disk reads: 32 MB in 2.86 seconds =11.19 MB/sec
---
The best SCSI drives are roughly twice that transfer rate, but 11MB/s is
fast enough for my jobs.
Tom
--
Tom Klok
Systems Administration Paralynx Network Operations
Opinions expressed are personal; I do not speak for my employers.