At least as of raidtools-0.90...
The problem stems from how the raidtools determines which drives to use for the
RAID plex (I won't go technical here). But, basically if you get in a
situation in which your drive configuration changes (i.e., add or remove a
drive), the raid detection attempts to determine how the drive IDs of the disks
have changed. In my experience, this sometimes is wrong and RAID plexes will
not come up completely and will be downgraded. This can be a particular pain
with 90GB plexes which take several hours to resync. Things which help: if a
drive fails, always replace a bad disk with the same ID and always keeps your
drives sequential (i.e., SCSI ID 0,1,2,3). Another things to do it to upgrade
your raidtab file with new IDs if drives get rearranged and rewrite the
superblocks (this cannot be done with the off-the-shelf raidtools).
On 13-Jan-2000 Hossein S. Zadeh wrote:
> On Wed, 12 Jan 2000, yukon wrote:
>
>> For future use (and depending on if you've got autoraid compile -
>> something I'd advise against if you value your data), just use
>> raidstart /dev/md0.
>
> May I ask why you advise against autodetection of software raids?
>
> Hossein
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