Date: Wed, 22 Aug 2007 10:37:29 +0200 From: Michel Talon <talon@lpthe.jussieu.fr> To: freebsd-questions@freebsd.org Subject: Re: GEOM, Vinum difference Message-ID: <20070822083729.GA93337@lpthe.jussieu.fr>
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Rakhesh Sasidharan wrote: > Another (related) question: both gvinum and the geom utilities like > gmirror and gstripe etc provide for RAID0, RAID1, and RAID3. Any > advantages/ disadvantages of using one instead of the other? There has been a polemic between Greg Lehey and PJ Dawidek about the comparative advantages of raid3 and raid5. You can find the exchanges on Google. One example being: http://arkiv.freebsd.se/?ml=freebsd-performance&a=2004-08&t=227183 As far as i remember there are arguments showing that raid3 is better than raid5 both in terms of speed and of data security. It seems that raid5 has mostly a hype factor for him, but i may err. Anyways it is for such reasons that in the modern geom system, raid3 has been implemented and not raid5. But vinum has been ported to the geom framework for the benefit of old users, or of people who like it. For example if you are using FreeBSD-4 or DragonFlyBSD, vinum is the standard tool, and you may prefer getting expertise in just one tool. Finally none of these raid systems is really good, both for performance and security. If you are concerned with your data and want good write speed, you must buy enough disks and use raid 10. Another important factor is ease of use. The geom tools, gmirror, gstripe, graid3, etc. are *very* easy to use. The documentation in the man pages is clear, sufficient for doing work, and not too long. On the contrary, vinum was traditionaly documented in a very hermetic way. But more recently, Greg Lehey has provided a very clear chapter of his book on his web site which can be recommanded, but is not short. Note the documentation is a critical aspect of such systems because its lack may bite you in case a disk crashes and you need to adopt correct procedures under stress. Also for some time the gvinum stuff was extremely buggy, and was completely non functional when i tried it. I hope it is fixed now. -- Michel TALON
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