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

[Allan Jude]

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.

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.


-- 
Allan Jude

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