svn commit: r304142 - head/usr.sbin/bsdinstall/partedit

[Nathan Whitehorn]

On 08/18/16 02:50, Dag-Erling Smørgrav wrote:
> Nathan Whitehorn <nwhitehorn at freebsd.org> writes:
>> OK. In which configurations? My Dell servers, for instance, don't do
>> this. How are they set up? What drivers are being used? Is this
>> something that affects passthrough disks, RAIDs, disk images?
> Most LSI MegaRAID controllers don't have real passthrough, only JBOD.
> You can query the drive with "camcontrol identify passX", but the
> controller does not report a stripe size for the volume (mfidY).

OK, so it's mfid. That's good to know.
>
>> The point is that *if the reported stripe size is wrong*, more things
>> than partition alignment in the installer will suffer for it.
> It's not wrong, it's non-existent, and I'm getting really tired of
> repeating myself.

For some drivers, this interface is not implemented. This is a bug, 
which should be fixed.

>
>> Fixing the installer with a bandaid in the run-up to a release is
>> fine, but *we need to fix the underlying problem*.
> We can't, because hardware sucks, and I'm getting really tired of
> repeating myself.
>
> DES

As am I. Here's the point:

We have a mechanism (GEOM stripe size) for drivers to supply a default 
alignment to userland. If we think we can get that right, great. If we 
don't think we can get it right, the default system policy in the 
absence of real information from drivers should be modified to report a 
number that we think is more likely to be safe than the current defaults 
(the logical sector size, usually 512 bytes) and potentially tunable by 
the user. Hacking the userland tools one-by-one to impose their own 
default policies to override the systemwide one is, while a perfectly 
valid stopgap right before a release, a ridiculous long-term solution. 
Do you disagree with any of that?
-Nathan