On a side note, I have seen two vendors who do offer IDE raid solutions. I can't remember who off hand, but they're out there...
On Wed, 5 May 1999, mark wrote:
On Wed 5 May, 1999, tkaczma@gryf.net wrote:
The price differences between SCSI and IDE are not that significant anymore, but I was wondering why someone didn't come up with and IDE
Wrongo. SCSI is still way more expensive than EIDE. It's just the EIDE disk are meant for cheap-and-cheerful low-requirements users and SCSI occupies the middle-high disk market. But we're talking about a VLE filer here, so we can make different assumptions, maybe.
appliance. The argument that I would come up with is that you can only have 2 devices on one bus, much too few for a RAID 5 set. This also
Bzzt. Irrelevant, add more busses because EIDE busses are also quite cheap.
applies to your request for a 3 disk appliance. The power of striping comes from the number of drives. The more drives you add the smaller the parity overhead. With 3 drives 33.3 ... % is "wasted" on parity. With 14 drives the "waste" goes down to about 7%.
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.
(And no, I'm not interested in the philosophical war of IDE vs SCSI. Fact: IDE is currently cheaper than SCSI. Fact: I want this box to be cheap. Check and mate. :))
I agree. But I'd do things slightly differently.
No mate, and probably not even check. SCSI drives are not THAT much more expensive anymore. You must remember that you can have only 2 IDE 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).
on the bus, among other limitations. The money you save in drives will probably be made up in the complexity of the controllers and software. Everything costs money, the drives are only a fraction of the cost.
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).
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.
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 (just back up all memory - don't have separate NVRAM, we're talking small and compact here).
Given a K6-3 or Celeron and DOT this baby would cost quite a bit less in parts costs than the latest and greatest filers, but wouldn't be an embarrassment to NetApp (of that I'd be quite quietly confident).
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.
-- End of excerpt from tkaczma@gryf.net
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