On Mon, 19 Mar 2012 16:04:34 -0700 Chris Francy <zoredache@xxxxxxxxx> wrote: > I am seeing a different array size with mdadm --detail and --examine, > and I don't understand why. > > I have seen this on a production systems, but I created an array in a > VM for testing purposes, and I am seeing the same results. > > I have a 5 device RAID10 with created like so. It has 5 members 8GB > each. Which I believe should result in an array size of ~20GB. > > mdadm -v --create /dev/md0 --assume-clean \ > --level=raid10 --layout=o2 --raid-devices=5 \ > --chunk=64 \ > /dev/sdb2 /dev/sdc2 /dev/sdd2 /dev/sde2 /dev/sdf2 > > mdadm --detail reports an array size of ~20GiB > > root@debian:~# mdadm --detail /dev/md0 > /dev/md0: > Creation Time : Fri Mar 16 16:06:09 2012 > Raid Level : raid10 > Array Size : 20960960 (19.99 GiB 21.46 GB) > Used Dev Size : 8384384 (8.00 GiB 8.59 GB) > > mdadm --examine reports an array size of ~16GiB > > root@debian:~# mdadm --examine /dev/sdb2 /dev/sdd2 /dev/sde2 /dev/sdf2 > /dev/sdb2: > Avail Dev Size : 16769024 (8.00 GiB 8.59 GB) > Array Size : 33537536 (15.99 GiB 17.17 GB) > Used Dev Size : 16768768 (8.00 GiB 8.59 GB) Thanks for the report. There seems to be a rounding error in mdadm when calculating the size to report for --examine. The value for --detail is of course correct. I'll try to get it fixed in the next release. Thanks, NeilBrown > > Most of my testing was done on a Debian squeeze system, but I manually > compiled and installed mdadm 3.2.3 and I also saw the same confusing > output from a Gentoo based livecd with a recent kernel. > > The full output of the mdadm output is pasted available here. > http://paste.debian.net/160057/ > > The array in the VM seems to work fine, I was able to create a > filesystem and store data on it. But the output from the --examine is > confusing. > > The same is true with the use Dev size `8384384 (8.00 GiB 8.59 GB)` > versus `16768768 (8.00 GiB 8.59 GB)`. > > Chris Francy > -- > 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
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