[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 11:50 AM, Ed W wrote:
>> One of the snags of md RAID1 vs RAID6 is the lack of checksumming in the
>> event of bad blocks.  (I'm not sure what actually happens when md
>> scrubbing finds a bad sector with raid1..?).  For low performance
>> requirements I have become paranoid and been using RAID6 vs RAID10,
>> filesystems with sector checksums seem attractive...
>
> Except we're using hardware RAID1 here and mdraid linear.  Thus the
> controller takes care of sector integrity.  RAID6 yields nothing over
> RAID10, except lower performance, and more usable space if more than 4
> drives are used.

How would the control ensure sector integrity unless it is writing
additional checksum information to disk? I thought only a few
filesystems like ZFS does the sector checksum to detect if any data
corruption occurred. 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.