ZFS and DMA read error

Arthur Chance freebsd at qeng-ho.org
Thu Sep 3 14:02:40 UTC 2009

Mark Stapper wrote:
> I ordered a "spare" drive so I'll wait until it arrives, replace the
> faulty drive with this one by dd-ing data from one to the other (I have
> only 4 SATA ports so I can't do "zpool replace").

zpool replace has two forms

	zpool replace pool old-device new-device


	zpool replace pool device

The latter is for when you pull the old drive and put the new one on the 
same {S,P}ATA port because you've no free ports. I did that a couple of 
weeks ago when one of my raidz drives fried (in its warranty period!) 
and it worked like a dream. I did a zpool replace and then a zpool scrub 
  to make sure everything was OK because of this section of the zpool 
man page:

     Scrubbing  and resilvering are very similar operations. The differ-
     ence is that resilvering only examines data that ZFS  knows  to  be
     out  of  date (for example, when attaching a new device to a mirror
     or replacing an existing device), whereas  scrubbing  examines  all
     data to discover silent errors due to hardware faults or disk fail-

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