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Date:      Thu, 18 Aug 2016 22:15:12 -0600
From:      Warner Losh <imp@bsdimp.com>
To:        Allan Jude <allanjude@freebsd.org>
Cc:        =?UTF-8?Q?Dag=2DErling_Sm=C3=B8rgrav?= <des@des.no>,  Nathan Whitehorn <nwhitehorn@freebsd.org>, src-committers <src-committers@freebsd.org>,  "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>,  "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>
Subject:   Re: svn commit: r304142 - head/usr.sbin/bsdinstall/partedit
Message-ID:  <CANCZdfrGhFTR5sbKRiehXQhhexX=KfW920NJJg0Je=yigqEyEA@mail.gmail.com>
In-Reply-To: <2f9fb04c-7ec4-be40-8fcb-0cf74bb56859@freebsd.org>
References:  <201608150930.u7F9UL1V069576@repo.freebsd.org> <e3454e8e-5d98-5bec-21de-8ea0db2b9b08@freebsd.org> <861t1n6749.fsf@desk.des.no> <581c856c-826b-529e-c9c6-a397fb679708@freebsd.org> <86wpjf4eun.fsf@desk.des.no> <8cb3fa1a-50cb-e238-d006-b98a628d446d@freebsd.org> <86k2ff4cxs.fsf@desk.des.no> <b96c3f91-faaa-2552-b4da-2d0d382461af@freebsd.org> <86fuq24d8s.fsf@desk.des.no> <2f9fb04c-7ec4-be40-8fcb-0cf74bb56859@freebsd.org>

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On Thu, Aug 18, 2016 at 6:56 AM, Allan Jude <allanjude@freebsd.org> wrote:
> On 08/18/16 05:50 AM, Dag-Erling Sm=C3=B8rgrav wrote:
>> Nathan Whitehorn <nwhitehorn@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).
>>
>>> 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.
>>
>>> 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
>>
>
> Which makes more sense:
>
> A) If stripesize =3D=3D 0, use some sane value like 4096

I don't like this.

> B) Some other combination that uses the reported stripe size, unless it
> is 0, in which case it uses 4096 (or some other value controlled by a
> different new sysctl)

Don't like this so much.

> C) create kern.geom.min_stripe_size with a default of 512, but users can
> set 4096 if they use only 4k devices. (doesn't really solve the problem
> for the installer)

Default it to 4k, and allow users to set it to 512. If the drive
reports < this value
report this value instead. You'll need to make this a tunable. Then the upp=
er
layers wouldn't care. There's a small chance that some SD cards might be
reporting values that are too large. But I think it is confined to SD cards=
 and
if I see too many more I'll do something specific in the SD driver.

Warner



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