[Dovecot] Better to use a single large storage server or multiple smaller for mdbox?

[Emmanuel Noobadmin]

On 4/12/12, Stan Hoeppner <stan at hardwarefreak.com> wrote:
> On 4/11/2012 9:23 PM, Emmanuel Noobadmin wrote:
> I suppose the controller could throw an error if
>> the two drives returned data that didn't agree with each other but it
>> wouldn't know which is the accurate copy but that wouldn't protect the
>> integrity of the data, at least not directly without additional human
>> intervention I would think.
>
> When a drive starts throwing uncorrectable read errors, the controller
> faults the drive and tells you to replace it.  Good hardware RAID
> controllers are notorious for their penchant to kick drives that would
> continue to work just fine in mdraid or as a single drive for many more
> years.

What I meant wasn't the drive throwing uncorrectable read errors but
the drives are returning different data that each think is correct or
both may have sent the correct data but one of the set got corrupted
on the fly. After reading the articles posted, maybe the correct term
would be the controller receiving silently corrupted data, say due to
bad cable on one.

If the controller simply returns the fastest result, it could be the
bad sector and that doesn't protect the integrity of the data right?

if the controller gets 1st half from one drive and 2nd half from the
other drive to speed up performance, we could still get the corrupted
half and the controller itself still can't tell if the sector it got
was corrupted isn't it?

If the controller compares the two sectors from the drives, it may be
able to tell us something is wrong but there isn't anyway for it to
know which one of the sector was a good read and which isn't, or is
there?