> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
> boun...@opensolaris.org] On Behalf Of Stephan Budach
> I am always experiencing chksum errors while scrubbing my zpool(s), but
> I never experienced chksum errors while resilvering. Does anybody know
> why that would be? 

When you resilver, you're not reading all the data on all the drives.  Only 
just enough to resilver, which doesn't include all the data that was previously 
in-sync (maybe a little of it, but mostly not).  Even if you have a completely 
failed drive, replaced with a completely new empty drive, if you have a 3-way 
mirror, you only need to read one good copy of the data in order to write the 
resilver'd data onto the new drive.  So you could still be failing to detect 
cksum errors on the *other* side of the mirror, which wasn't read during the 

What's more, when you resilver, the system is just going to write the target 
disk.  Not go back and verify every written block of the target disk.

So, think of a scrub as a "complete, thorough, resilver" whereas "resilver" is 
just a lightweight version, doing only the parts that are known to be out-of 
sync, and without subsequent read verification.

> This happens on all of my servers, Sun Fire 4170M2,
> Dell PE 650 and on any FC storage that I have.

While you apparently have been able to keep the system in production for a 
while, consider yourself lucky.  You have a real problem, and solving it 
probably won't be easy.  Your problem is either hardware, firmware, or drivers. 
 If you have a support contract on the Sun, I would recommend starting there.  
Because the Dell is definitely a configuration that you won't find official 
support for - just a lot of community contributors, who will likely not provide 
a super awesome answer for you super soon. 

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