Re: RAID6 grow unexpected results

[Neil Brown <nfbrown@novell.com>]

[-- Attachment #1: Type: text/plain, Size: 1833 bytes --]

Liwei <xieliwei@gmail.com> writes:

> Hi list,
>     I tried growing a RAID6 array by executing the mdadm --add and
> mdadm --grow --raid-devices commands. Usually that should run fine and
> I can continue with pvresize.

That is incorrect.  You cannot run "pvresize" until the reshape
completes.

>
>     This time however, the actual usable raid array size did not
> change even though reshape begins. In my confusion, I decided to
> reboot. That didn't solve the problem (and apparently the reshape was
> interrupted, but mdadm shows the grown array as clean?)

Clean is expected.  It will be in an intermediate state, part has
reshaped to extra devices, part is still the original.

>
>     I then executed mdadm --grow --size=max, which seemed to have
> increased the array size, but apparently by too much. Now I'm getting
> "attempt to access beyond end of device" errors for each of the
> component drives. A new reshape operation has also begun, which I
> expect would fail as the array size is now too big.

"--size" isn't the same as "--array-size".
"--size" is the size of the component devices to use.

The "attempt to access beyond end of device" errors are unexpected but
presumably related o the "--size=max".  Maybe the 'max' chosen was too
large.  That suggests a bug somewhere.
You probably want to reduce that size back to where it was.

>
>     What did I do wrong and how can I remedy this?

Could we start with "mdadm --examine" status of all devices, "mdadm
--detail" of the array, and all kernel messages that could possibly
relate to the array since you first started this exercise?

NeilBrown

>
> Liwei
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 818 bytes --]