> 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