On Wed, 5 May 1999, mark wrote:
Wrongo. SCSI is still way more expensive than EIDE.
Just an example of RETAIL market prices for drives.
9.1GB EIDE Ultra DMA / 66 AC29100 7200RPM 9.5NS 2MB Buffer 3 Year Warranty
$188
9.1GB 3391WD SCSI Wide Differential.
$219
about 15% difference in price. I wouldn't call that much. I think you're a bit out of touch with the market.
Bzzt. Irrelevant, add more busses because EIDE busses are also quite cheap.
Custom design boards cost a lot of money for small quantities. Increased levels of code complexity also costs more money to develop and maintain. Bzzt. Why don't you start a company and do it, if it's so great and you have such a great niche for the product.
Parity overhead in terms of space maybe, but computation goes up linearly at best and might go up higher (reconstructing blocks from parity when a disk blows). Tradeoff time.
Computation time might be negligible to the I/O time, thus restoring parity on 10 drives may not be much slower than on 2. Also with just 2 drives you may not be saturating the pipe meaning that you're wasting time in between operations on the bus with 2 drives. Again, restoring parity on 10 drives might not be much slower than 2 drives.
Oh yeah they are. Here in the UK I spent 360quid on an UW 9GB Seagate (end user price) where a 10GB UDMA EIDE drive cost 190quid (end user price).
See prices above. Just because you chose to pay that much for a drive doesn't prove that that is a fair market price.
I've seen PCI-EIDE controllers advertised for about the same as SCSI host adapters, but I'd put them together on the motherboard with an integral network interface (10/100Base-TX).
Exactly, but with one IDE controller you can have only 4 devices on 2 buses, with 1 SCSI narrow you can have 7 with a wide 15. The speed differences might not be great. I dunno, I haven't looked at the latest speed specs of SCSI vs. ATA.
Performance on the SCSI is a bit better but not *that* much better. I'd bet that a good board designer could easily put 3 EIDE controllers on a PCI bus, giving you (4 devices per EIDE controller, last time I counted) 12 disk connections.
Custom designs cost much more money.
The motherboard could have the EIDE connections, one cheap integral SCSI host adapter for tapes, one network interface and one set of battery-backed memory.
Why SCSI. There are IDE tapes out there.
You could make the mboard quite small and make the whole thing into a single rack-mount shelf/deskside tower style thing, with the disks presented at the front and the power-supply, motherboard access, serial-line, floppy drive, network connector and SCSI connector round the back.
Custom design again. I don't think you realize how much a board shop will charge you for a custom M-board. Add to it the costs of short run assembly.
I'm not saying it can't be done, but why break one's back to suit the low end market with marginal margins (pun intended). Use SCSI and semi-OTSCs and sell your product at a reasonable markup to people who can afford it. For others there are the Cobalts and etc. of this world. Look into Cobalt, you may find what you want. A cheap low-end server.
Tom