On Jan 15, 2012, at 8:49 PM, Bob Friesenhahn wrote:

> On Sun, 15 Jan 2012, Edward Ned Harvey wrote:
>> Such failures can happen undetected with or without ECC memory.  It's simply
>> less likely with ECC.  The whole thing about ECC memory...  It's just doing
>> parity.  It's a very weak checksum.  If corruption happens in memory, it's
> I am beginning to become worried now.  ECC is more than "just doing parity".

It depends. ECC is a very generic term. Most "ECC memory" is SECDED, except for 
high-end servers and mainframes.

> http://en.wikipedia.org/wiki/Error-correcting_code
> http://en.wikipedia.org/wiki/ECC_memory
> There have been enough sequential errors now (a form of corruption) that I 
> think that you should start doing research prior to posting.

I've been collecting a number of ZFS bit error reports (courtesy of fmdump -eV) 
and I have
never seen a single-bit error in a block. The errors appear to be of the 
overwrite or stuck-at
variety that impact multiple bits. This makes sense because most disks already 
correct up to
8 bytes (or so) per sector.
 -- richard

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