Date: Sat, 27 Jun 1998 17:50:06 -1000 From: richard@pegasus.com (Richard Foulk) To: Greg Lehey <grog@lemis.com>, Stefanos Kiakas <stefanos@ringworld.uniscape.com>, freebsd-hardware@FreeBSD.ORG Subject: Re: RAID and FreeBSD Message-ID: <199806280350.RAA25683@pegasus.com> In-Reply-To: Greg Lehey <grog@lemis.com> "Re: RAID and FreeBSD" (Jun 28, 1:01pm)
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} > Having had a software RAID system fail I would recommend against them. } } What would you have done if you had had a hardware RAID system fail? } ?? Fix it or replace it. } > With hardware RAID there is greater assurance that once you've used } > it for a few weeks or months that it will remain consistent. As } > part of an OS kernel (drivers, etc.) uncertainty revisits every time } > the system software is upgraded, patched or changed in some way. } } I suppose if you don't upgrade your RAID box, you don't change old } bugs for new. The same applies to a kernel, of course. Even if you upgrade your RAID box (which happens much less often than OS upgrades in my experience), the system is simpler and the RAID is much more likely to be just like the vendors units. With OS-based software RAID you'll almost never have a configuration just like the vendor's. } } > Hardware RAID may be a touch slower, but it's more trustworthy. } } I'm not contesting this, though I'm surprised you think it's slower. } I would expect it to be faster, since you have another processor to } which you can offload the work. At the moment, of course, we don't } have anything to go on. It depends. Most of the hardware implementations I have experience with have been somewhat slower than their software counterparts. The interface is the bottleneck. It's easier to add additional I/O channels to the same logical device when the RAID resides within the OS. If you have a 10-Gig partition spread over five drives you could have as many as five host SCSI interfaces pumping data simultaneously. With an external (hardware RAID) system it's difficult to utilize more than one I/O channel for the full 10-Gigs. Richard To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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