Date: Thu, 15 Jul 1999 11:52:41 +0100 (IST) From: Nick Hilliard <nick@iol.ie> To: radams@siscom.net Cc: mjacob@feral.com, hardware@FreeBSD.ORG, stable@FreeBSD.ORG Subject: Re: Fibre Channel Controller Message-ID: <199907151052.LAA19073@beckett.earlsfort.iol.ie>
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> Have you used these? If so, how does the FC route compare to say U2W SCSI? > Something about a little piece of fiber running my drives makes me feel all > warm and fuzzy. A pal of mine who designs FC cards mailed me about this a few months ago. Nick -- | Nick Hilliard | nick@iol.ie | | Tel: +353 1 6046800 | Advanced Systems Architect | | Fax: +353 1 6046888 | Ireland On-Line System Operations | <...> but lets face it if you think 80MBytes/sec is nearly as good as 100Mbytes per second, you have to realise a few things 1) you don't get anything close to 80Mbytes/sec because SCSI doesn't share the bandwidth very well. Whereas with Fibrechannel 80MBytes per/second sustained to/from disk is achievable with anyone's adapter and up to 96 with the better ones. When you compare IOs/sec SCSI falls away much faster. HP have managed 33000 IOs from one FC loop. 2) Just you try to configure 30 drives on a SCSI system and then try the same on Fibrechannel. Then put all the drives in another room and see if you can make it work. 3) Multi-Initiator on SCSI? Don't make me laugh. Every FC drive has two ports as standard. Multi-Initiator is built in. [...] 5) Lost packets on Fibrechannel does not mean lost data. It is true that Class 3 is like IP, it doesn't have ACKs and this is a problem because it can cause timeouts. But compare that with SCSI where if you have cabling problems (and I know all about SCSI cabling problems) you just can't make it work at all. 6) Fibrechannel drives do not consume 50% more than SCSI drives unless you want to compare current SCSI drives with old FC ones. [...] 8) FC is bidirectional and is meant to be dual loop so really you have 400Mbytes per second if you want to compare numbers. By the time Ultra160 is stable 2Gb FC links will be available. Where has SCSI to go then? 80Mhz I don't think so. 2Gb transceivers are readily available and 4Gb transceivers are well on their way. So what would I buy for my PC, well UltraSCSI of course, unless <company> gives me an FC cabinet. Then again if I was buying a couple of terabytes then I would go FC, mirroring (RAID1) not RAID5 because drives are cheap and write performance is better. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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