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Rev

thanx for replying. i forgot to mention that i did call --examine on the device and nothing was printed about chunk-size. here's an example output. is it my mdadm version (v3.1.4) or metadata version that makes the difference?
– Huang Tao
Commented Aug 30, 2011 at 8:38
1

I've seen two thoughts on this. One, since RAID 1 doesn't stripe, chunk size is irrelevant. In another, it's only relevant to reads/seeks. My guess is, it wasn't set since it's RAID one, and if it has a value, it's the default 64k
– OldWolf
Commented Aug 31, 2011 at 16:03
Your output says you're using RAID1. See the comment and two links I've added above.
– OldWolf
Commented Aug 31, 2011 at 16:13
3

i'm aware that i was using the 64k default chunk-size. i've read the man pages and the wikipedia article before i asked the question. however, since "the chunk-size specifies how much data to read serially from the participating disks", it does matter for raid 1 arrays, doesn't it? i mean, it's supposed to take chunk-size into consideration tuning the filesystem lying on the array, right?
– Huang Tao
Commented Aug 31, 2011 at 17:05
You'd probably want the chunk size to be small enough so that application requests get distributed over drives and big enough to not spend a lot of time splitting or assembling data streams.For SSDs, it's get a bit more complicated as the internal erase block size of the drive will impact performance. A chunk size of 1 MiB or more can be a good choice.
– Joachim Wagner
Commented May 12 at 12:19

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