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What should I do to determine chuck size of existing raid arrays. I'm using software raid created by mdadm.

I've been probing around for a while and can't find the right utility to that job.

mdadm --detail /dev/md/0

mdadm --examine /dev/sda0


cat /proc/mdstat

doesn't say any thing about chunk size.

cat /sys/block/md0/md/chunk_size

returns 0

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Looks like you can run

mdadm -e /dev/sda1  

or similar against one of the devices in the array. It will print the superblock and lists the chunk size there.

See the third grey section here

EDIT: See here and here on chunk size in RAID1

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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 Aug 30 '11 at 8:38
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 Aug 31 '11 at 16:03
Your output says you're using RAID1. See the comment and two links I've added above. – OldWolf Aug 31 '11 at 16:13
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 Aug 31 '11 at 17:05

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