Date: Mon, 6 Mar 2000 18:31:29 -0800 From: Scott Hess <scott@avantgo.com> To: james@icorp.net Cc: freebsd-questions@FreeBSD.ORG Subject: Re: RAID/config questions Message-ID: <20000306183129.B2525@river.avantgo.com> In-Reply-To: <38C45697.D736070F@icorp.net> References: <38C45697.D736070F@icorp.net>
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On Mon, Mar 06, 2000 at 07:08:39PM -0600, James wrote: > 1. What is the best RAID controller/model to use? (for either setup) > I've been pretty happy with Adaptec and FreeBSD's support of Adaptec > controllers, so I would prefer to stay with Adaptec but don't know about > their RAID offerings.. Keep in mind that Adaptec RAID controllers aren't really the same as normal Adaptec SCSI controllers, as I learned to my chagrin under Linux. Unfortunately, I don't have any FreeBSD experience with them, or experience less than a year old. To be honest, I'd probably go with a cheaper SCSI controller and use software RAID for a workstation type system (which it sounds like you're talking about). > 2. Which will give me better performance? RAID or RAID5? I > know RAID5 will give me more disk space, but is there any significant > i/o performance cost? My most recent experience was with an external SCSI-SCSI RAID controller attached to an Adaptec differential host adapter on FreeBSD3.3. With six drives plus a hot-spare, I found that RAID5 (5 drives plus parity) and RAID1+0 (3 drives worth of mirrorred and striped data), the performance was pretty similar. The deciding factor was that when we pulled a drive, rebuilding under RAID5 really degraded performance (it could carry about 1/3 the tps relative to when it wasn't degraded), while rebuilding under RAID1+0 was only marginally noticable. On the other hand, this external controller has 32M of non-volatile cache, plus on-board CPU, so it might make RAID5 seem better than it would on a simpler card. > And generally speaking, how much of a performance degredation may I > see (if any) in going from a non-raid SCSI to a RAID or RAID 5 setup? Hardware RAID shouldn't degrade performance at all. Software RAID0 or RAID1 shouldn't have much impact, RAID5 can have more because it has to actually muck with the data. Later, scott To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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