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Technology Stocks : The New QLogic (ANCR) -- Ignore unavailable to you. Want to Upgrade?

To: R Verchota who wrote (23283)	7/11/1999 3:35:00 PM
From: George Dawson	Read Replies (1) \| Respond to of 29386

R Verchota, I think the writer misses some key points on the risks/benefits of FC over SCSI: System performance is contingent on more than just bandwidth, but also on I/O. A recent analysis in InfoStor (Goldman S. SCSI and Fibre Channel: A Comparison, InfoStor June 1999: pp 32 - 33) yields the following comparisons: SCSI 3,000 I/Os per second for 8KB files (IOs) UltraSCSI 2 7,813 IOs UltraSCSI 3 12,987 IOs FC (1 GB) 10,870 IOs FC (2 GB) 21,740 IOs The author points out that the usual 15 disks on a SCSI bus are limited to 106-110 accesses / disk spindle or a total of 3,000 accesses per set of disks. This puts all of the SCSI buses at or above the performance level of the disks. The cost factor is also significant because you can use for example 3 SCSI buses which are a lot less expensive that 2 FC buses. The main advantage for FC comes in with larger disk arrays. The limiting factor for FC disk arrays is latency and this becomes a significant factor at about 40 disks. In terms of cabling, SCSI is a parallel bus requiring multiple cables. FC is a serial bus and only one cable is required. The writer is correct that FC supports several network protocols. There are SCSI switches out there, but the last time I looked they were much more expensive than FC switches and would eliminate the cost advantages of using SCSI buses and disks. Technocrat's post from yesterday is also relevant here - FC disks are also coming down in price especially with the competition between Seagate and IBM. On the Jaycor/Adaptec situation - Jaycor has acquired FC rights from Adaptec and recently announced new PCI to FC HBAs based on that technology. George D.