When constructing a RAID with mkraid there is no way to limit the size of the resulting pseudo-device. When creating partitions, you can specify a size to fdisk, but it is possible that you end up creating a partition that is a little bit larger because it rounds up. mkraid for a mirror creates a pseudo-device which is the minimum of the sizes of the component partitions. Similar minimums are used when constructing RAID5. scenario: you ask fdisk for a 64G /dev/sda1 and get a 64.01G /dev/sda1. You ask fdisk for a 64G /dev/sdb1 and get a 64.01G /dev/sdb1. You build a raid /dev/md0 from /dev/sda1 and /dev/sdb1. It is 64.01G /dev/sdb fails. You replace it with /dev/sdc. you ask fdisk for a 64G /dev/sdc1 and get a 64.00G /dev/sdc1. raidhotadd chokes because /dev/sdc1 is not large enough to participate in the mirror. Reproducible: Always Steps to Reproduce: raidhotadd /dev/md0 /dev/sdc1 Actual Results: /dev/md0: can not hot-add disk: too small disk!
Not a Gentoo-specific problem, please report feature requests upstream.
The HOMEPAGE referenced in the sys-fs/raidtools-1.00.3-r6.ebuild is http://people.redhat.com/mingo/raidtools/ The page this points at does not appear to be much of an "upstream", eh?
