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Date:      Thu, 18 Aug 2016 23:33:36 -0600
From:      Warner Losh <wlosh@bsdimp.com>
To:        Nathan Whitehorn <nwhitehorn@freebsd.org>
Cc:        Warner Losh <imp@bsdimp.com>, Allan Jude <allanjude@freebsd.org>, =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no>, 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:  <880977BE-F00F-4188-A978-F292AB452C79@bsdimp.com>
In-Reply-To: <081362ef-ff4a-61d5-46e4-9a4cf8b699ee@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> <CANCZdfrGhFTR5sbKRiehXQhhexX=KfW920NJJg0Je=yigqEyEA@mail.gmail.com> <081362ef-ff4a-61d5-46e4-9a4cf8b699ee@freebsd.org>

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> On Aug 18, 2016, at 11:21 PM, Nathan Whitehorn =
<nwhitehorn@freebsd.org> wrote:
>=20
>=20
>=20
> On 08/18/16 21:15, Warner Losh wrote:
>> 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).
>>>>=20
>>>>> 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.
>>>>=20
>>>>> 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.
>>>>=20
>>>> DES
>>>>=20
>>> Which makes more sense:
>>>=20
>>> A) If stripesize =3D=3D 0, use some sane value like 4096
>> I don't like this.
>>=20
>>> 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.
>>=20
>>> 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 upper
>> 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.
>>=20
>> Warner
>>=20
>>=20
>=20
> That sounds good to me and I think can clean up a lot of code and =
potential foot-shooting. Who is planning to make the patch? I'm happy to =
do anything that would be helpful.

The patch is super-easy, but I need to get the concept validated and =
make sure that it does not have unintended side effects.

Warner


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