From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ralph =?iso-8859-1?q?Pa=DFgang?= Subject: Re: Which raid card to buy for Sarge Date: Wed, 31 Mar 2004 22:42:49 +0200 Sender: linux-raid-owner@vger.kernel.org Message-ID: <200403312242.49462.ralph@debianbase.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Content-Disposition: inline To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Am Mittwoch 31 M=E4rz 2004 21:50 schrieben Sie: > > If would not use the "raid" feature of the Highpoint cards, because= it is > > only software raid and not so performant as a hardware raid. If you= don't > > need a Oh, my sentence should have started with: "I would not use ..." not wit= h:=20 "If.." :) > please don't say things like this. HW raid is *NOT* generally > faster or better than software raid.=20 I never said that it is "better" than software raid, because I don't th= ink so.=20 I am using mdadm myself and I think it is great software (together with= the=20 kernel code). But normaly a real hardware raid is without a doubt faste= r than=20 a software raid. But the most servers/computers don't really need hardw= are=20 raid, because the don't produce this huge amount of data. With the sentence you quoted from me, I only wanted to say, that I woul= dn't=20 use the software of the highpoint card to build a software raid, becaus= e it's=20 closed software (if I remeber right) and it is only there to fake the p= eople,=20 because highpoint doesn't say clearly (on the product box for example) = that=20 it is a "software" raid IDE100/133 Card (so it should be called: IDE Ad= apter=20 with software raid tools). If you are not so familiar with this kind of= stuff=20 you maybe even think years later that this is a real hardware raid=20 (espacially under windows). I would use the HPT Adapter only as normal ide adapter and build a soft= ware=20 raid, or if I need the performace I would use a hardware raid, but only= then.=20 I don't have to much money, like the most peole, so I don't buy useless= =20 stuff. (in my private I still use a pentium 60 as gateway with firewall= , ntp=20 server, some other small thinks) But you are right, only a few servers really need a hardware raid. The = most=20 are idleing the most time :) But many customers (and I am working for a= isp)=20 wants a hardware raid (even if they haven't good a clou of such stuff a= nd=20 doesn't really need this for their server). The words: "hardware raid" = are=20 good for marketing... Its like ide and scsi drives :) And if a customer= wants=20 something it not always a good idea trying to convert him to another=20 solution. > yes, if you're building a=20 > quad-gigabit fileserver out of an old P5/100 you had sitting around, > you're not even going to start looking at sw raid. > > but for a normal FS config (dual opteron or xeon, >1GB ram, > 2-400 MB/s sustained disk throughput), software raid is The Right Cho= ice. i never said that software raid is slow! I just said that hardware raid= is=20 faster... That's a difference :) I never would say that a amd athlon xp= is=20 slow, but without a doubt a amd athlon 64 is faster :) > - speed: it's easy to do hundreds of MB/s with sw raid. it's surpris= ingly > hard to break even 100 MB/s using sw raid. > > - you don't pay through the nose for a crappy embedded processor > to do your parity calculations > > - hw raid *does* reduce the amount of PCI-X traffic you generate, > but do you really care, at 1 GB/s? it's not about me and if I care... I only tried to help Jay choosing th= e right=20 solution for his raid setup... I only said that I think the hpt adapter= s are=20 fakes raid adapters, because it's software raid, and that if HE wants=20 hardware raid, he should take another adapter. > - sw raid *does* consume some host CPU cycles, but do you care, > given that this is a fileserver? > > - give me mdadm and normal userspace tools over some wheel-reinventin= g > hw raid configurator. > > - you've probably got the hardware to fix an exploded sw-raid server > already in your office (other computers, normal disk controllers, etc= ). > replacing that hw raid card WILL take more than 30 minutes, obviously= will > take money, and will eventually become impossible. I also said this... I had some broken disks in hardware raids and in so= ftware=20 raids in the last 2 years. Both solutions have advantages and disadvant= ages=20 again: - Advantage: its faster to fix a broken sw raid setup. It's only a shut= down,=20 change disk, restart, rebuild the array in the background. In the hardw= are=20 raid you normaly have to rebuild the array in the bios and so the compu= ter is=20 offline for at least that time. - Disadvanage: Sometime linux crashes if a hard disk in an array broke.= I=20 don't know for sure why this happens, but I guess it has something to d= o with=20 the ide channel which is marked as busy and never gets useable again. A= crash=20 after a disk broke down never happend to me on a hardware raid. I know that this a kernel ml for the software raid in linux, but hey, = I only=20 told jay what are advantages and disadvantaged in the hpt software raid= , the=20 linux mdadm software raid and a a hardware raid is. I think there was n= othing=20 wrong about it and I even think that we have more or less the same opti= nion=20 in sw/hw raids. Once again: i am using mdadm myself and think that the linux software r= aid is=20 great, no question... I never wanted to say something else. So don't=20 understand this wrong, but _even_ hardware raid has the right to life .= )) --Ralph - To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html