This is part of The Pile, a partial archive of some open source mailing lists and newsgroups.
Subject: Re: Software RAID, other RAID questions. From: Shane Owenby <shane@collab.net> Date: Thu, 24 Feb 2000 14:26:03 -0800 On Thu, Feb 24, 2000 at 01:25:20PM -0800, Eric Fixler wrote: > > If anyone has any experince with this stuff any pointers on the following > would be helpful and well-appreciated: read the archives of the linux-raid list on vger. > - In an SMP setup, what can I expect of software RAID vs hardware RAID > performance? [I'm looking for anectodal approximation, benchmarks not > really necessary]. I ran it on a dual pII 400Mhz with 70+ Gb on raid 5 using 2.2.12ac2 IIRC. The performance was excellent, and you don't have any of the heartaches of hardware RAID. (read: It served up a lot of mp3's and ppl never complained about the performance, downtime, etc). > - Do people like using the software RAID tools on Linux? Do they make life > lot more complicated? trivial once you understand what to do with them. Make sure to read the RAID Howto b4 you start...as you can cause damage. Also there is a bug which I reported (search for shane@raleigh.ibm.com in the archives...*cough my previous employer*) where if you have 2 disks go down on a raid 5 array the array is still marked 'rebuilding' or something when in fact it should be marked as down or damaged, etc... All that is in the archive.... In short have fast CPU's, recent kernel, good disks, RTFM, then relax. === Subject: Re: Software RAID, other RAID questions. From: Derek Vadala <derek@usfca.edu> Date: Thu, 24 Feb 2000 15:44:32 -0800 (PST) On Thu, 24 Feb 2000, Eric Fixler wrote: > I found some really good information about RAID at > http://linas.org/linux/raid.html but couldn't really find much telling me > about the state of software RAID on Linux with the 2.2.x kernels. > It's probably not your fault that you can't find anything. Version maintainence has been bad and you really have to dig to peice together a history of software RAID on Linux. I got this note from Ingo Molnar last week: "hi Derek, there are some news that might be worth mentioning in your article. I've started merging the 'latest' RAID patches into 2.3, the biggest and most important part is already in 2.3 as of 2.3.43. I also became the official maintainer of the RAID subsystem as of 2.3.43. This means that 2.4 will have the greatest and latest RAID code. So if you have any questions/suggestions/bug reports, feel free to ask me :-)" Basically what he's saying is that until 2.3.43 the RAID code distributed with the kernel is old and needs to be patched with the newest version. I think that 0.41 is what's currently distributed while 0.90 is the current version. So as of 2.4, all stable releases will have the latest code from Molnar. For now you need to grab the 0.90 patches and the raidtools. Tools: ftp://ftp.kernel.org/pub/linux/daemons/raid/alpha/raidtools-19990824-0.90.tar.gz 2.2.X: ftp://ftp.kernel.org/pub/linux/daemons/raid/alpha/raid0145-19990824-2.2.11.gz 2.0.37: ftp://ftp.kernel.org/pub/linux/daemons/raid/alpha/raid0145-19990824-2.0.37.gz Yup. Confusing as hell. > - Do people like using the software RAID tools on Linux? Do they make life > lot more complicated? As opposed to? The software RAID tools are essential. They are not complicated and silly like the software RAID tools on say Solaris or IRIX. ==== Subject: Re: Software RAID, other RAID questions. From: Michael Higashi <mhigashi@hooked.net> Date: Thu, 24 Feb 2000 16:52:24 -0800 (PST) On Thu, 24 Feb 2000, Eric Fixler wrote: > Hi all. I am trying to spec out some new server machines for a client and > I'm trying to figure out what to do re:disks. > > I found some really good information about RAID at > http://linas.org/linux/raid.html The link at that site for the Software RAID howto actually points to the _old_ howto, for raidtools version 0.50. You really, really want the _new_ howto, which goes with raidtools version 0.90: http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/ There is also a linux-raid mailing list that might be useful to you. There's an archive of the list at: http://kernelnotes.org/lnxlists/linux-raid/ > but couldn't really find much telling me about the state of software > RAID on Linux with the 2.2.x kernels. Software RAID used to require a patch to the kernel. As of kernel 2.2.13, that raid code was merged into the kernel source. I believe that changes were made in the raid code in the 2.3.x kernels. If you create a raid partition under kernel 2.2.x, it may not be mountable if you upgrade the kernel 2.3.x due to differences in the raid superblock. I'm still trying to confirm that. > - Do people like using the software RAID tools on Linux? Do they make life > lot more complicated? One of the neat things you can do with software raid is to mirror the swap partition. Normally if the swap partition dies due to disk failure while Linux is running, the system is guaranteed to crash. With a mirrored swap, your system keeps on running. ===