I found this old message, it may help. ====================================== http://www.corpit.ru/mjt/mdctl.c - a very small utility similar to raidtools
Note it will not work correctly in the situation described. Or at least it may not work. For the same reason as original code does not work: "renamed" devices in 2.4 vs 2.6.
With raidstart (and this utility follows it logic), it is the kernel who is reading the raid superblock, opening devices and assembles the array. Most important part is the superblock: kernel will pick up any devices found there (by major/minor number). When booting 2.4 and 2.6, or when your devices are using dynamically-assigned numbers, that numbers may be different on next reboot, so kernel will not be able to find all required devices.
While mdadm tries to examine all superblocks and find all devices in between the ones listed on command line, in the superblock or ones that are really present on your system at any given time (--scan; depends on your mdadm.conf also).
So when you expect your device names/numbers to be instable between reboots, it's best to use mdadm together with --scan and proper mdadm.conf or with all possible devices listed in command line. Mdassemble by Luca Berra will be useful here too.
/mjt
P.S. Please trim original message somehow when replying.
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