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Date:      Wed, 28 Jun 2017 19:01:26 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-doc@FreeBSD.org
Subject:   [Bug 220343] The manual page for mpt should inform about disk size limitations of most/all supported controllers
Message-ID:  <bug-220343-9@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D220343

            Bug ID: 220343
           Summary: The manual page for mpt should inform about disk size
                    limitations of most/all supported controllers
           Product: Documentation
           Version: Latest
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: Documentation
          Assignee: freebsd-doc@FreeBSD.org
          Reporter: sebastian@rostwald.de

Most (if not all?) controllers supported by the mpt driver have firmware-
and/or hardware-induced limitations on their supported disk/array/LUN size =
-=20
mostly <2TB. As these limitations are well below typical sizes of modern ha=
rd
drives, it would be sensible to inform the user about these limitations in =
the
manual page.


While most controllers truncate the usable/reported size to the supported s=
ize,
some might wrap around and cause serious data corruption. See for example t=
he
3ware 7000/8000 series in this archived KB article:
http://web.archive.org/web/20120326110817/http://kb.lsi.com:80/Knowledgebas=
eArticle16481.aspx

>From my own experiences, behaviour of many controllers with such limitations
upon attaching bigger disks is best described as "undefined" - I've seen
anything from not recognizing/reporting the disks, locking up at boot to se=
vere
data loss when reaching the supported size limit.

Due to the possibility of data loss on controllers that wrap around address
space, I suggest adding the information about these limitations and possible
data loss within a WARNING section of the manual page.


Draft/suggestion:

----

WARNING

Most controllers supported by the mpt driver suffer from limitations on
supported disk size (mostly <2TB). While *most* controllers will only trunc=
ate
usable disk size, others might behave unexpectedly and cause severe data lo=
ss.
Refer to the specifications of your chipset and firmware version for
information about supported disk size.

----


--=20
Regards,
Sebastian

--=20
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