> On Wednesday, June 08, 2011 09:00:48 PM mcclnx mcc wrote:
>> We have DELL server with MD1000 Disk array in it. O.S. is CENTOS 5.5.
>> Recently every time MD1000 "patrol read" start I will get "media error"
>> messages on /var/log/message file.
>>
>> I use MD1000 "slow initialize" to initialize "bad disk" and NO error.
>> After "slow initialize" finish, I manually "startup patrol read". I
>> continue get "media error" on /var/log/message.
>>
>> Anyone know what difference between "slow initialize" and "patrol read"?
>
> Only Dell really knows what they mean by it.
>
> But here are some random thoughts:
>
> * Slow init may write all of the disk during init but maybe:
> 1) no errors happen during write
> 2) it notices an error but retries silently
> 3) it notices an error but has sucky error reporting
Yes, both can be true. I guess it's simply because a disk which writes on
a bad sector/block just silently remaps it and goes on because it's
considered fixed.
> * Patrolread (may) compare parity data and report this as "media error"
> (a type of error slow init probably wouldn't detect)
> * The I/O pattern of patrolread compared to slow init provoks an error
I always tought patrolread just tries to read the whole disk to detect
sleeping bad sectors/blocks. Maybe it also checks consistency on the RAID
level but I'm not sure.
Simon
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