Date: Mon, 13 Dec 1999 22:20:49 -0700 From: Brett Glass <brett@lariat.org> To: David Scheidt <dscheidt@enteract.com> Cc: Terry Lambert <tlambert@primenet.com>, noslenj@swbell.net, chat@FreeBSD.ORG Subject: Re: dual 400 -> dual 600 worth it? Message-ID: <4.2.0.58.19991213220839.00c869e0@localhost> In-Reply-To: <Pine.NEB.3.96.991213220754.55242A-100000@shell-2.enteract. com> References: <4.2.0.58.19991213200556.0473c1e0@localhost>
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At 09:12 PM 12/13/1999 , David Scheidt wrote: >There are those of us who have machines that need long cables. One of the >boxes I manage has disks that are 15 meters away from the CPU cabinet. There will always be some of these, but they'll be statistically rare. >If >you need to have hundreds of disks, you can't have silly cable lengths. SCSI can really only have 7 disks per cable. (Yes, I know, you can extend the addressing to get 15, or use logical units, but this causes problems with bus loading and also with contention for the bus.) Also, I'm sure you will agree that hundreds of spindles on one computer is not the norm. We shouldn't bog down our core standards because of one case that's several sigma off the low end of the probability scale. >Of >course, the next generation box will be all Fibre Channel, but still. Even >on my home box, I have a need for greater than 1 metre bus lengths. No problem! Use the shorter cables within the disk array and then use SCSI or Fiber Channel -- on the other side of the RAID controller -- for the longer-haul connections. Also, putting that much disk space on a single machine may not be a good idea. If it has that much data to serve up or search, it's probably going to be strapped for CPU cycles or network bandwidth. Depending on the situation, you might be better off distributing your files or databases and putting several disks (but not hundreds) on each server. This makes the system more failsafe, too: one bad CPU won't take down the whole operation. --Brett To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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