bin/164281: bsdinstall(8): please allow sysinstall as installer option

[Allan Jude]

On 2014-05-25 12:43, Nathan Whitehorn wrote:
> On 05/25/14 09:32, Allan Jude wrote:
>> On 2014-05-25 12:27, Nathan Whitehorn wrote:
>>> I'm (finally) integrating these patches now. Could you remind me what
>>> the point of the gnop is? I'm not sure I get it.
>>> -Nathan
>> The 'gnop -S 4096 <device>' makes a virtual device that has a sector
>> size of 4096 bytes. This causes ZFS to set ashift=12 even for devices
>> that mis-advertise (lie about) their sector size. There is no real harm
>> in using 4k sectors on a 512b sector device, but using 512b sectors on a
>> 4k device will cause write amplification (read-modify-write) since the
>> device will have to deal with it as a partial block update.
> 
> I think our ATA code mostly has this under control at this point.
> 
>> Additionally, the sector size can only be set at pool creation time,
>> even if you have have 512b sector devices, you'll want to create your
>> pool as 4k, so that in the future when you add additional devices, or
>> replace failed devices, the 4k sector devices will be supported. ZFS
>> complains loudly when you try to add mis-matched sector size devices to
>> a pool.
>>
>>
> 
> This is a good reason, even if the circumstances behind it are stupid.
> Is there really no way to handle this besides gnop? Can't we just fix ZFS?
> -Nathan
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Linux added an explicit option to the zpool, so you can just do:

zpool create -o ashift=12 mypool mirror disk1 disk2

There was some discussion about this in the OpenZFS group, but it was
usually cited as a reason why there was a need to for OpenZFS, to keep
the Linux version from diverging and adding a bunch of non-standard options.

I am not sure what the best option is. The gnop is only required while
the pool is being created, it doesn't need to be re-created in order to
import the pool etc, it is just to trick ZFS the first time.

-- 
Allan Jude

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