[dm-devel] Why it can not support more than 100 targets in 1 MD ?

[Kevin Corry]

On Thursday 01 April 2004 20:46, Ji Haitao wrote:
> I create a MD having 100 targets with dmsetup. IO error occurs when I
> access the 100th target. My operation steps are :
>
> 1.#create md
> sh> dmsetup create vd1 dmtable1
>
> 2.
> #access the 100th target
> sh> dd bs=512 count=10 if=/dev/zero of=/dev/mapper/vd1 seek=51380224
>
> #errors happen
> dd: writing `/dev/mapper/vd1': Input/output error
> 1+0 records in
> 0+0 records out

I ran your 100-target table on one of my systems. Did a dd of the entire 
device with no I/O errors. I'm running device-mapper.1.00.08 on a 2.6.5-rc3 
kernel.

> If I only have 99 targets in dmtable1, everything is OK when I access
> the 99th target. Why? If device-mapper can support more than 100 targets
> in 1 MD ?

> The configuration of my Linux host is:
> CPU: P4 1.4G
> MEM: 512M
> Kernel: 2.4.21
> device-mapper.1.00.05
> dd (fileutils) 4.1.9

1.00.05 is a bit out-of-date. I'd suggest upgrading to device-mapper.1.00.09 
(upgrade both the tools and the kernel patches) and see if the problem 
persists.

-- 
Kevin Corry
kevcorry at us.ibm.com
http://evms.sourceforge.net