Date: Tue, 13 Apr 1999 16:53:43 +0200 (CEST) From: Remy Nonnenmacher <remy@synx.com> To: ken@plutotech.com Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: Huge SCSI configs Message-ID: <199904131453.QAA35693@rt2.synx.com> In-Reply-To: <199904130422.WAA09582@panzer.plutotech.com>
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On 12 Apr, Kenneth D. Merry wrote: > Remy Nonnenmacher wrote... >> I am looking for advices about building a fearly huge SCSI config. >> >> The config would be : >> >> - 4 SCSI chains (2x3950U2W planned) > > That should work okay, as long as you use -current or -stable *after* March > 23rd. I've got one in my test box, and it seems to work fine. I haven't > pushed it much, though. > OK. Sorry for this late (but ever unanswered question) : what are the known limits in term of SCSI chains, number and size of disks and sizes of filesystems ? Anyone ? > One thing to be careful about is what sort of slot you put this thing in. > If you get a motherboard with only 32-bit slots, you need to make sure that > the back end of the PCI slots is thin enough to handle a 64-bit PCI card. > >..... OK. Still looking for 64 bits PCI MB. >> - 12 18.2 GB per chain (48 totals disks) > > Well, first off, make sure you get IBM or Seagate, and make sure you get > one of their high end drives. (not that they're making low-end 18 gig > drives yet, AFAIK) I've had direct experience with the 18G Seagate > Cheetah II's and IBM Ultrastar 18XP's. They both work fine. My guess is > that the IBM Ultrastar 18ZX would work well, too. > > You should be okay with most any 18G IBM or Seagate disk. > > But 12 per chain? Assuming these are all Ultra2 LVD, you're still pushing > things a bit as far as SCSI bus bandwidth is concerned. For instance, the > IBM Ultrastar 18ZX runs at about 23MB/sec on the outer tracks according to > IBM's web site. > > With that sort of performance, you wouldn't be able to get maximum > performance out of the disks if had more than 3 on an Ultra 2 chain. > Drives would be CCDed or Vinumed by groups of four, one per chain. Each drive divided into three parts, the outer, intermediate and inner cylinders to provide 3 different performance rings. Due to environmental constraints, there are two prefered drives : IBM 18ES or Quantum Atlas4 all two 1 inches. > You'll also have to start worrying about PCI bus bandwidth and memory > bandwidth, depending on what sort of motherboard you get. > > So, one question I have is this -- are you looking for maximum disk > performance, or just a lot of disk space? If you're just looking for a lot > of disk space, why not go with 36GB drives? NECX (www.necx.com) is selling > IBM Ultrastar 36XP's for $1400. The Ultrastar 18ES is selling for $775. > So, it would be cheaper to go with a 36G drive. (FWIW, I know that the > 36XP's work just fine, but I haven't seen any 18ES drives yet. I'd imagine > they work fine as well.) > 36.4 Gigs are all 1.6 inches and won't (probably) fit. 50.1 Gigs are too youngs (bad exp with Seagate on early drives, and probably unaffordable) and would lead to less R/W heads. >> - one Gigabit ethernet link > > Isn't there only one gigabit ethernet driver (Alteon?) at the moment? You > should probably ask Bill Paul how it works. You may also want to ask David > Greenman about this, since I think he mentioned on -current a while back > that he was working on a Gigabit Ethernet driver as well. > Seen it. Packet-engine also provide one. >> - SMP (Quad-Xeon or Bi-P2) > > Considering the monster you're trying to build, I'd say go for a board > that'll get you 64-bit PCI and high memory bandwidth. My guess is that a > Quad Xeon board from Intel might do the trick. Ask Mike Smith about these, > they had (have??) one at Walnut Creek, I think. > Thanks for you reply. It seems pretty clear that PCI bandwidth will be the real problem. I know for sure that it have been a problem on the GigaEth. case and it will be a botleneck point with two (or more) fast SCSI cards running high-end drives. Also, Xeon machines do not appear to be the real killers Intel pretends but SC450NX (or the HP version using 64 bit PCI) machines goes pretty well in my (rackable) constraints. Thanks again. RN. ItM To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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