Re: limits on raid

[Dan Merillat]

> For raid5 on an array with more than 3 drive, if you attempt to write
> a single block, it will:
>
>  - read the current value of the block, and the parity block.
>  - "subtract" the old value of the block from the parity, and "add"
>    the new value.
>  - write out the new data and the new parity.
>
> If the parity was wrong before, it will still be wrong.  If you then
> lose a drive, you lose your data.

Wow, that really needs to be put somewhere in 120 point red blinking
text.  A lot of us are used to uninitialized disks calculating the
parity-on-first-write, but if linux MD is forgoeing that
'dangerous-no-resync' sounds really REALLY bad.  How about at least a
'Warning: unlike other systems this WILL cause corruption if you
forego reconstruction' on mkraid?
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/