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Re: scsi-ide
Let's get this clear:
1. All modern EIDE disks use DMA transfer whenever possible. SCSI
interfaces use the same, or, rare (high end) interfaces, use mapped
caches, which are indeed faster, but cost the world.
This means, that the overhead for a SCSI transfer and for an EIDE transfer
of the same data will be in favor of EIDE on the same hardware class.
There are EIDE adapter cards that cache and RAID up to 4 drives. Thay cost
less than the equivalent SCSI solution.
2. SCSI devices do not have different 'bus speeds'. Neither have EIDE
devices, but Ultra-DMA devices only work with their own kind in enhanced
mode on one same interface. Fast SCSI devices can, indeed, be operated
together with slower ones.
3. SCSI configuration and driver setup has been a major problem since
forever on the PC architecture, while it works extremely well on others
(example: Mac). EIDE has only given problems when generations chaged, and
ppl. had to get used to new settings.
4. The only REAL benefit of SCSI is in RAID/mirroring and CD-write
operations and backups that can be done w/o the intervention of the
computer, by using us-mastering controllers. The price of implementing
this is so high, that many people simply buy one more computer to do all
that and use a network to connect the things...
5. While all EIDE devices are somewhat robust against 'pulling the power
plug', SCSI devices are notorious for losing data under the same
conditions. This means that a SCSI installation MUST run on an UPS. Add to
this the increased power requirements of SCSI and you wind up with a scary
price... The fact that 'pros' choose SCSI, does not mean that the average
PC users (even power user's) installations must choose the same, excepting
when he is: a) rich b) keeps up with trends at any cost c) reads too many
advertising materials, and too little real-world performance comparisons.
The latest trend in making EIDE CD-writers reflects precisely the fact,
that the manufacturers have understood that they cannot sell that many
SCSI devices to low end users, as they would have liked to.
6. The so-called fire wire (IEEE 1394) will put an end to this within
foreseeable time. It is likely that in consumer PCs, SCSI is going to 'go'
first, because too many people use EIDE, and the ones who choose SCSI will
upgrade fast to IEEE 1394 for the same reason they went for SCSI when they
did. This will leave IEEE 1394 and EIDE to compete for a while. Although I
believe that local-bus EIDE or something like that is coming rather soon.
Technically, makeing the transition from EIDE to ultra-wide local bus (32
or 64 bit) eide is nothing for the drive manuafcturers.
On Wed, 3 Dec 1997, S. Schapiro wrote:
> Hi,
>
> >> 4. SCSI is much better than IDE
> >Huh ?
> >SCSI better (not MUCH, but better) tham IDE in
> >multiuser and server enviroment . Nothing more .
>
> I don't think so: SCSI is better the moment you want to connect more than
> one decive (perhaps runningat different bus-speeds) and the moment you find
> out just how much CPU you IDE-disk is using up. Besides that you waste less
> of the rare interrupts when you connect more stuff (disks, cd-roms, a tape
> or a MO, a scanner etc.) to your computer.
>
> Schlomo
>
>
Peter Lorand Peres
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