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

[Wolfgang Denk <wd@denx.de>]

Dear Chris,

In message <2C80C970-FE4F-4CFE-8F40-48BE14F3140F@colorremedies.com> you wrote:
> 
> > The mismatch number is not divisible by 16, yet your chunk size is
> 16KB. It is divisible by 4 and 8, so I'm going to guess that the
> physical sector size is 4096 bytes. If correct, I'm coming up with a
> maximum of 346GiB worth of sectors may be adversely affected, assuming
> every sector in the mismatch count is bad (which is probably not true,
> but could be).
> 
> Since the upgrade to Fedora 18 for this particular RAID 6, can you
> estimate how much data has been written to the array? Could it be in the
> 90GiB to 350GiB range?

No.  Much less has been written.  But then, your calculation above is
wrong - these are 510 byte sector disks.

> man 4 md says the same, for raid 5 and 6, mismatches are not expected to
> be software problems, but much more likely hardware. But if it's true
> that the OP's problems started exactly with the upgrade to Fedora 18,
> that it could be a device driver. What HBA is being used?

Correct, the hardware has not been changed, and has been running fine
for many months before,

Two of the systems use a Marvell Technology Group Ltd. MV88SX6081
8-port SATA II PCI-X Controller; the third system uses a LSI Logic /
Symbios Logic SAS1068E PCI-Express Fusion-MPT SAS controller.

Best regards,

Wolfgang Denk

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