Re: Huge values of mismatch_cnt on RAID 6 arrays under Fedora 18

[Wolfgang Denk <wd@denx.de>]

Dear Piergiorgio,

In message <20130129175720.GB2396@lazy.lzy> you wrote:
>
> my personal opinion would be to confirm
> *all* the data is OK, if you can.

Unfortunately I have no easy way doing this.  Most of the data are
working trees of software builds, or build results, so I have no
checksum or other information.  But all files I accessed so far, of
where I was able to check, were actually correct.

> Uhm, as mentioned, it would be nice to
> find a specific error slot...
> Well, not so nice, but this would point
> to an HW problem.

I am not a friend of quick conclusions in cases like this, but I think
that hardware issues are very unlikely to hit with identical effects
simultaneously on 3 different machines in 2 different locations.


> > OK, add more hardware details...
> > 
> > A: Supermicro X8SAX mainboard, Core i7 CPU 950 @ 3.07GHz, 24 GB RAM
> > H: Supermicro X8ST3 mainboard, Xeon CPU W3565  @ 3.20GHz, 24 GB RAM
> > X: Supermicro X8SAX mainboard, Core i7 CPU 950 @ 3.07GHz, 24 GB RAM
>  
> What does the kernel log says about the choosen
> RAID6 algorithm?

System A:

[   57.121902] raid6: sse2x1    7660 MB/s
[   57.138892] raid6: sse2x2    8687 MB/s
[   57.155890] raid6: sse2x4    9789 MB/s
[   57.155891] raid6: using algorithm sse2x4 (9789 MB/s)
[   57.155892] raid6: using ssse3x2 recovery algorithm

System H:

[   45.360607] raid6: sse2x1    7753 MB/s
[   45.403614] raid6: sse2x2    8777 MB/s
[   45.445612] raid6: sse2x4    9773 MB/s
[   45.472547] raid6: using algorithm sse2x4 (9773 MB/s)
[   45.503347] raid6: using ssse3x2 recovery algorithm

System X:

[   51.471793] raid6: sse2x1    3996 MB/s
[   51.517657] raid6: sse2x2    4851 MB/s
[   51.566579] raid6: sse2x4    4960 MB/s
[   51.598831] raid6: using algorithm sse2x4 (4960 MB/s)
[   51.638697] raid6: using ssse3x2 recovery algorithm


Note: I remembered that I converted yet another machine which has a
(smaller) RAID6 array (4 x SAMSUNG SpinPoint F1 HE502IJ) on a less
powerful PC (Gigabyte P35-DS3R mainboard, Intel Core 2 Duo CPU E6750
@ 2.66GHz, 8 GB RAM).  This shows NO problems (so far).  Here I have:

[   11.253015] raid6: sse2x1    1902 MB/s
[   11.270021] raid6: sse2x2    2296 MB/s
[   11.287274] raid6: sse2x4    3171 MB/s
[   11.287533] raid6: using algorithm sse2x4 (3171 MB/s)
[   11.288127] raid6: using ssse3x2 recovery algorithm


If you can draw any conclusions from that - I can't.

Best regards,

Wolfgang Denk

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DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
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