Assembling me a new rig - novice questions

[Umfriend]

Oh, I don't care you triple posting, the info I get here is invaluable. I am preparing now already to have some time to order parts so that I can assemble it after X-mas.

I ain't got the guts yet, but soon I'll ask whether to buy an ATi 7000 LE or a GF2-MX400?

As said, I'll need to do some reading and thinking, thx sofar!

Actually, I do very much mind cable lenght limitations (which arew also with SCSI, but far less) and devices. The thing is, I bought the AHA2940U2W with the idea that I would hook up a scanner, DVD/RW sometime later. Scanner is now USB and no SCSI DVD to be seen. May main fear is that it'll die soon. Used to be SCSI was first to get things, now it's the other way around I think.

And yeah, SCSI BIOS setup takes a lot of time too. This is another thing, a want the shortest boot time possible (I hate to wait).

I think my old C-64 took abou 1 second, and that baby ran it 1 mhz.... Why can't I beat that? What is actually taking so long? Ah well, guess that's another thread.....
Umf

[WyWyWyWy]

Hmm... so nobody notices the main point in using SCSI is that it consumes less (way less) CPU cycles and memory than ATA drives?

[mutz]

...yeah but what I've found out is you go SCSI or you don't. I've got a SCSI card in there generally hanging things up for a scanner and a Plextor CD. Some day I'm going to dump it. It's no longer in the stream of things. I could hang up to 12 IDE drives on my mobo, if I needed to...

[Ribbit]

Originally posted by WyWyWyWy
Hmm... so nobody notices the main point in using SCSI is that it consumes less (way less) CPU cycles and memory than ATA drives?

Damn, I'm a SCSI bigot and even I missed that! To make up for it, have some very unscientifically generated numbers:

System setup: Tyan Thunder K7, 512MB PC2100, Single Athlon MP 1900+ CPU, Linux 2.4.19 (with various patches).
Maxtor D540X 160GB 5400RPM drive on primary IDE channel (hdparm -t gives ~35MB/sec), only device on channel. DMA, IRQ unmasking etc. all set.
Seagate X15-36LP 36GB 15K-RPM drive on m/b SCSI channel B (hdparm -t gives ~58MB/sec), channel shared with another such drive.
Idle system.

IDE drive:
dd if=/dev/ide/hd/c0b0t0u0 of=/dev/null &
top shows 24-25% CPU usage.

SCSI drive:
dd if=/dev/sd/c1b0t0u0 of=/dev/null &
top shows 27-28% CPU usage.

Tentative conclusion: SCSI uses very little more CPU to transfer about 65% more data. If anyone's bothered, I'll repeat this on my Tiger MP with 10K-RPM SCSI and 7200RPM IDE. (And maybe my 486 with 7200RPM SCSI and 5400RPM IDE. )

I don't know about the memory advantage, though. A good SCSI disk driver will have code to take advantage of tagged command queueing (another big SCSI advantage ) and scatter-gather, etc., while an IDE disk driver is closer to just dumbly (is that a word?) forwarding the OS requests to the disk. But there won't be much in it memory-wise anyway.

[WyWyWyWy]

Try write instead of read I think you'd see a even bigger difference.

dd if=/dev/zero of=/mnt/scsidrive count=300000000
or something like that!

[Ribbit]

Ah, but that way it becomes more complex to interpret because you involve the filesystem layer, and the way I've got that box set up, it would also involve EVMS' LVM and RAID layers. That said, I might give it a go later if I can make it a reasonably fair test.

[Wombat]

Don't get the ATI 7000. Crappy ugly card (ask RichL). Not a big fan of the MX cards either, but it's the lesser of two evils here.

[rugger]

SCSI vs IDE in a nutshell (maybe, since I have no doubt that I will end up fighting over almost every point here )

SCSI: Faster drives, noisier drives, more devices, expensive, long cables, constantly changing standards, wow factor, some people swear it is more effecient than IDE, requires an adapter for most motherboards.

IDE: Slower (but adequete) drives, quieter drives, fewer devices, cheap, annoyingly short cables, constantly changing standards, stupidly boring, sometimes devices don't like each other, Software for the most part can't automaticly optimize it properly.

[WyWyWyWy]

Originally posted by rugger
SCSI vs IDE in a nutshell (maybe, since I have no doubt that I will end up fighting over almost every point here )

SCSI: Faster drives, noisier drives, more devices, expensive, long cables, constantly changing standards, wow factor, some people swear it is more effecient than IDE, requires an adapter for most motherboards.

IDE: Slower (but adequete) drives, quieter drives, fewer devices, cheap, annoyingly short cables, constantly changing standards, stupidly boring, sometimes devices don't like each other, Software for the most part can't automaticly optimize it properly.

VERY true indeed sir!!!

[Ribbit]

You forgot to mention that EIDE drives are generally larger (not that it's anything to do with the interface, but you did mention faster/noisier SCSI drives). And SCSI is more efficient, it's not just a bunch of old-timers telling old wives' tales I'm not that old anyway...