Disk Errors during boot and run time.

[Konstantin Svist]

Bryn M. Reeves wrote:
> On Fri, 2009-03-06 at 12:22 +1300, Paul Ward wrote:
>   
>> # ls /boot
>> ls: reading directory /boot: Input/output error
>>     
>
> What's in dmesg at this time?
>
>   
>> I have been told that the disks use multipath but I have no experience
>> of this to date.
>> I know the disks are on a SAN but as yet have not been able to locate
>> them using the IBM SAN manager.
>>
>>     
>
>   
>> Linux version 2.6.18-53.1.21.el5PAE
>>     
>
> So, RHEL5.1?
>
>   
>> (brewbuilder at ls20-bc2-13.build.redhat.com) (gcc version 4.1.2 20070626
>> (Red Hat 4.1.2-14)) #1 SMP Wed May 7 08:56:33 EDT 2008
>>     
>
>   
>>   Vendor: IBM       Model: 1814      FAStT   Rev: 0916
>>   Type:   Direct-Access                      ANSI SCSI revision: 05
>>     
>
> So it's an IBM FAStT SAN? These are active/passive storage arrays that
> require use of a multipath hardware handler to properly manage switching
> between the active and passive paths and preventing I/O being sent to a
> controller that cannot handler it.
>
> The I/O errors that you see are a result of things trying to access the
> passive paths (e.g. partition scanning, lvm label scanning, udev/hal
> probes etc.).
>
> RHEL5.1 included the old device-mapper hardware handlers. These will
> only take effect once multipath has configured the devices and only
> handle path switching in the event of a path failure (i.e. you'll still
> see I/O errors if something tries to access one of the underlying paths
> directly rather than via the multipath device map).
>
> RHEL5.3 introduces the scsi device handler framework as a replacement
> for the device-mapper hardware handlers (this appeared upstream in
> 2.6.26).
>
> Whether you decide to update or not it's probably worth carefully
> checking the current multipath configuration on the system as this is a
> very common area for configuration mistakes.
>
> Regards,
> Bryn.
>
>
>   

I don't think this is hardware-specific. I've seen this problem on
desktop-grade hardware, using either IDE or SATA drives (single 300GB
Seagate). Mine happened while I was using cloning software CloneZilla
(don't remember which version, right now).
I'll post more details if/when i run into the problem again...