I have a 2.0.35 system patched with raid0145-19981110-2.0.35, using
raidtools-19981105-0.90, with drives sda and sdb.
I'd like to add sdc and sdd and build a RAID-5 array from sdb, sdc and sdd;
but not lose the data currently on sdb.
My thought was to build a "degraded" RAID-5 array with sdc and sdd, copy
the data from sdb to that array, then raidhotadd sdb to the array, which
would then be whole.
How do I convince mkraid to initially build a "degraded" array? It
complains that raid_disks + spare_disks != nr_disks if I dont list three
devices and doesn't like /dev/null as the third disk (says cant get device
size).
I suspect that simply backing up is the easiest way. However, I like
puzzles.
Warning: I haven't done the following, it's just a guess. No
warranty implied :) You probably need additional steps, this is just
a rough outline.
0) reorganize the SCSI IDs to bring the existing sdb to be sdd
1) remove the power from sdd
2) define the array with sdb, sdc and sdd.
3) start the array, it should be degraded
4) clear any data on array
5) make sure that any daemons for reconstruction are inactive (other
wise your data is toast)
6) add power to sdd
7) get kernel to recognize sdd with ECHO add drive command mentioned in docs
8) mount that drive somewhere and copy away
9) reboot and restart array
Again, a backup to someplace is probably less effort and safer.
