ZFS RAID 0+1 Throwing Checksum Errors

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Mon Nov 9 19:40:03 UTC 2015


On Mon, 9 Nov 2015, Tim Gustafson wrote:
>
> I'm wondering if the problem is that the scrub is calculating the
> checksum for the data on gpt/zfs0, and while that's happening, some
> data is updated by Apache or MySQL, and then checksum for the data on
> gpt/zfs1 is calculated, which now doesn't match, and therefore the
> scrub is reporting an error.  Is that possible?

This is not possible.  ZFS uses Copy On Write (COW) such that existing 
data blocks and metadata are not overwritten.  Data is always written 
to unused free space.  The writes are done as part of a transaction 
group, and scrub will not see new data until the transaction group is 
completed.

> If that's not it, could this be a bug?  Or should I be worried about
> my SSDs?  What additional data would be helpful for me to share to
> diagnose this?

It could be the SSDs, the controller, cables, or power supply.  The 
problem might occur when the data is written, or when it is read back. 
If this is occuring on all of the SSDs then look for some shared 
component which might be causing the problem.

Bob
-- 
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/


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