Date: Fri, 30 Oct 1998 11:41:59 -0500 From: "Milliken, Scott" <MillikS@salestech.com> To: "'stable@freebsd.org'" <stable@FreeBSD.ORG> Subject: RE: RAID support in FBSD? Message-ID: <7B62F9E0DD56D111AADB006097A52FCC0465EA@STIUSATLCX1.salestech.com>
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Tom wrote: > Thats exactly what a SCSI-SCSI box is, and exactly what is being > talked > about. No need for your long description. > I know that and you know that, but I do believe that the original question was a very generic question from someone wanting to implement redundant technology in their university. Using terms like "SCSI-SCSI" with no explanation is rather ambiguous and doesn't really explain what the idea behind the technology is. My understanding was that this mailing list was a forum for people to learn more about FreeBSD, rather than a place to provide solutions with the least amount of words. > > Besides, a host based RAID controler takes RAID processor "offline" > too. > A DPT PM334 has a dedicated CPU and RAM, it just happens to be on a > PCI > card. > You're also limited by the speed of the PCI bus. If you're running a brand-spanking new motherboard with 100 MHz PCI then you *might* be able to come close to the performance of a lower end offline RAID (or SCSI-SCSI). Another advantage of offline RAID that wasn't mentioned and that an in-box RAID has a liability for is power loss. If your power supply goes out in the CPU then you can have corrupted data on the RAID, while if you lose power on the CPU with an offline box, it has a separate power supply. Most quality offline RAIDs have built in battery backup units and redundant power supplies to make sure that this doesn't happen - if the power is lost to the unit it flushes the cache and parks the heads on the drives. This has come in quite handy on more than one occasion (like when a tornado passed within 100 yards of the data center and ripped out all the power lines) when the UPS couldn't keep going indefinitely. I'm not trying to "slam" in-box RAID solutions, but if you're going to go - go all out. (To steal from the Hardee's commercial). If you can't afford an offline RAID solution, in-box is definitely better than no RAID at all. Scott A. Milliken IMS Health Strategic Technologies Systems Integration Group Atlanta, GA To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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