Date: Fri, 30 Oct 1998 10:17:09 -0500 From: "Milliken, Scott" <MillikS@salestech.com> To: "'stable@freebsd.org'" <stable@FreeBSD.ORG> Subject: RE: RAID support in FBSD? Message-ID: <7B62F9E0DD56D111AADB006097A52FCC0465E7@STIUSATLCX1.salestech.com>
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> ^^^^^^^^^^^^^^^^^^^ Usually, DPT is __very__ slow to operate in > degraded > mode, which makes it way unusable when such things happen. Since > the RAID (5, for instance) are supposed to be redundant/working even > when > in degraded mode, you want SCSI-SCSI box, something from > www.infortrend.com. > Let me as well issue the following phrase not proving it, since it'd > need > more than 2 pages of advocacy: since you will not really achieve > anything > more than 2mb/sec (values provided for ultra1-wide) in production > environment, > you really want SCSI-SCSI RAIDs which are much more easy to operate, > more redundant (see Tom's definitions/disadvantages list). > > I neither work for infortrend, nor dpt, of course. > > [Milliken, Scott] If you really want the fastest performance then you might want to consider a system that moves RAID completely offline from the server. At my office we use several Clariion (from Data General) RAID arrays, which are self contained boxes that have the RAID controller (or dual if you want multiple hosts or fail-over) built into the system. Other companies make similar systems where no specific drivers are needed on the host system. Basically the box appears to the host as a multi-LUN SCSI drive. You pop an Adaptec 2944 UW controller (differential SCSI, as most external arrays do not have single-ended options) and compile your kernel for that adapter. The neat thing about the Clariion is that it is configured through an ASCII terminal connection on the back of it, so you don't have to load up the proprietary software just to configure it (like the Compaq SMART 2 controllers). It also has five SCSI busses internal to the box, so you can have up to 5 members in a RAID grouping with each member on a separate bus. We have several of the 20 bay arrays and they are total screamers. I think you can now get 128MB read + 128 MB write cache on the controllers, but the 64 MB configurations we use are more than adequate. One other idea that I've come across but don't necessarily know if it's fluff or not, is that when you use an external array, you don't have to waste your pipeline's bandwidth with all of the parity data... so in theory it would seem that on a heavily used system reading/writing multiple RAID sets you could get a 20% boost from not having to transfer all that parity data. No, I don't work for DG or even a company that sells external arrays. I just find that they outperform any other system out there and they're the most OS independent solutions out there. Scott To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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