Am 01.10.2012 00:16, schrieb Chris Murphy: > > On Sep 30, 2012, at 3:08 PM, Stefan /*St0fF*/ Hübner wrote: > > >> Also off topic: 12 drives would be as "nearly unalignable" as 19 are. > > I'm not sure what you mean by unalignable. A separate question is if a 4K chunks size is a good idea, even with 24 disks, but I'm unsure of the usage and workload. > > [...] By that I mean that optimal alignment has to do with a reasonable chunk size and an amount of data disks that is/should be a power of two. If you made a databases commit chunk size 64k, you'd create maybe a raid6 of 6 drives with a 16k chunk size. That way you'd spare many many read-modify-write operations, as on every commit it'd write all 6 disks once and no rmw would happen. You'd also have to take care of proper partition placement. That probably is what you know as alignment. I just want to make it more concious that not only the placement of a data partition goes into alignment, also the size of a "normal" data packet relative to chunk size and amount of disks used. cheers, stefan -- 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
