On Thu, Dec 22, 2005 at 12:31:25PM +0000, Molle Bestefich wrote: > Since you say "we", I assume you're part of a very large corporation > and thus intend to RAID a whole bunch of disks. Go with RAID6 + a > couple of spares for that. If you intend to use really many disks, > make multiple arrays. (Not sure whether you can share spares across > arrays, but I think you can.) A recent foray through mdadm's code verifies this. If it noticies a failure and there is a spare, it attempts to migrate the spare to the array that needs it. Very cool feature! > I've seen lots of MD tests, but none that covered profiling MD's > random access performance. So I suppose that most hardware solutions > will do a lot better than MD here since they have been profiled with > this in mind. Well, it depends on the RAID level, disk, configuration, and how you're using it. In general, RAID 0+1 has better seek properties because reads can be done independantly from many disks. RAID5 is always going to be slow because n-1 disks need to all simultaneously read their stripe, and this can cause spindle contention. Of course, you lose more space to overhead as RAID 0+1 arrays grow... -- Ross Vandegrift ross@xxxxxxxxxxxx "The good Christian should beware of mathematicians, and all those who make empty prophecies. The danger already exists that the mathematicians have made a covenant with the devil to darken the spirit and to confine man in the bonds of Hell." --St. Augustine, De Genesi ad Litteram, Book II, xviii, 37 - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
