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From Josh Elser <josh.el...@gmail.com>
Subject Re: [VOTE] Apache Accumulo 1.6.1 RC1
Date Wed, 24 Sep 2014 17:41:09 GMT
The crux of it is that both of the errors in the CRC where single bit 
"variants".

y instead of 9 and p instead of 0

Both of these cases are a '1' in the most significant bit of the byte 
instead of a '0'. We recognized these because y and p are outside of the 
hex range. Fixing both of these fixes the CRC error (manually verified).

That's all we know right now. I'm currently running memtest86. I do not 
have ECC ram, so it *is* theoretically possible that was the cause. 
After running memtest for a day or so (or until I need my desktop 
functional again), I'll go back and see if I can reproduce this again.

Mike Drob wrote:
> Any chance the IRC chats can make it only the ML for posterity?
>
> Mike
>
> On Wed, Sep 24, 2014 at 12:04 PM, Keith Turner<keith@deenlo.com>  wrote:
>
>> On Wed, Sep 24, 2014 at 12:44 PM, Russ Weeks<rweeks@newbrightidea.com>
>> wrote:
>>
>>> Interesting that "y" (0x79) and "9" (0x39) are one bit "away" from each
>>> other. I blame cosmic rays!
>>>
>> It is interesting, and thats only half of the story.  Its been interesting
>> chatting w/ Josh about this on irc and hearing about his findings.
>>
>>
>>> On Wed, Sep 24, 2014 at 9:05 AM, Josh Elser<josh.elser@gmail.com>
>> wrote:
>>>>>> The offending keys are:
>>>>>>
>>>>>> 389a85668b6ebf8e 2ff6:4a78 [] 1411499115242
>>>>>>
>>>>>> 3a10885b-d481-4d00-be00-0477e231ey65:000000008576b169:
>>>>>> 0cd98965c9ccc1d0:ba15529e
>>>>>>
>>>> The careful eye will notice that the UUID in the first component of the
>>>> value has a different suffix than the next corrupt key/value (ends with
>>>> "ey65" instead of "e965"). Fixing this in the Value and re-running the
>>> CRC
>>>> makes it pass.
>>>>
>>>>
>>>>   and
>>>>>> 7e56b58a0c7df128 5fa0:6249 [] 1411499311578
>>>>>>
>>>>>> 3a10885b-d481-4d00-be00-0477e231e965:0000p000872d60eb:
>>>>>> 499fa72752d82a7c:5c5f19e8
>>>>>>
>>>>>>
>

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