Updated ashift optimization patch

[Richard Yao]

On 08/18/2013 10:26 PM, Justin T. Gibbs wrote:>> One thing we did here,
which would be good to see in this patch, is to add
>> an overall min system ashift as thie enables admins to configure pools
>> to be compatible with future disks they are likely to use e.g. min ashift
>> 12 (4k compatible). This could be left at 9 by default for max
compatibility
>> but personally I'd suggest 12.
>
> it would be nice to hear more consensus come out of the recent zpool
ashift discussions before doing something here.  Whatever that is, I
agree that the default should be 9 until someone fixes the RAIDZ space
penalty for going to 4k on 512N drives.
>
> --
> Justin
>

The default ashift is determined dynamically per top-level vdev by the
highest block_size reported by any member at creation time. There is no
fixed default ashift. However, many drives lie, so it could appear that way.

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