Dell Perc 6 disk geometry problem with RAID5 (both 6.3 final and 7.0 RC1)

[Aldas Nabazas]

On Jan 23, 2008 2:19 PM, John Baldwin <jhb at freebsd.org> wrote:

> On Sunday 20 January 2008 01:53:30 pm David Wood wrote:
> > Hi there,
> >
> > In message <20080120175819.GA52965 at owl.midgard.homeip.net>, Erik
> > Trulsson <ertr1013 at student.uu.se> writes
> > >On Sun, Jan 20, 2008 at 04:48:56PM +0000, David Wood wrote:
> > >> In message <9c1614e00801200608k49195944mf241b7b0aa6a48 at mail.gmail.com
> >,
> > >> Aldas Nabazas <freebsd.stable1 at gmail.com> writes
> > >>> We bought a new Dell PowerEdge 2950III with Perc 6/i and have the
> disk
> > >>> geometry problem using 6.3 final or 7.0 RC1. Seems that we are not
> alone at
> > >>> least one guy has similar problem reported earlier:
> > >>>
> > >>>
> http://unix.derkeiler.com/Mailing-Lists/FreeBSD/questions/2008-01/msg0
> > >>>0506.html
> > >
> > >I do not know if the mfi(4) driver has any problems with large disks,
> but it
> > >is however well known that fdisk(8) and bsdlabel(8) (the tools normally
> used
> > >to partition disks) have problems with volumes larger than 2TB.
> > >
> > >If you want to use volumes larger than 2TB then gpt(8) is the
> recommended
> > >way to partition the disks.  It is however doubtful if the BIOS in your
> > >system will allow you to boot from a gpt(8) parttioned volume which is
> > >best solved with having a separate - smaller - boot volume where the OS
> > >itself is installed.
> >
> > Erik's reminder is timely for those with >2TB volumes.
> >
> > You must use gpt and not fdisk on any disk, be it a single drive (in the
> > future, at least!) or a virtual disk on a RAID setup that are bigger
> > than 2TB. It may be wise to use gpt on any virtual disk that you might
> > grow to 2TB or larger in the future, so long as you're not needing to
> > boot from that virtual disk.
> >
> > fdisk will not work properly with 2TB and larger volumes - the MBR /
> > partition table setup can't cope with these large volumes.
> >
> >
> > You can't boot from a GPT volume - that's a limitation of the BIOS
> > architecture. There is some thought about using EFI on x64 hardware in
> > the future (EFI is used on ia64 hardware; GPT is part of EFI), but we're
> > not there yet. This isn't just about adding GPT support to the BIOS -
> > the whole BIOS setup is wedded to MBR.
> >
> > If you need to boot from a >2TB array, create two virtual disks - one
> > smaller than 2TB to boot from (and use MBR on that), then the residue
> > can be GPT.
>
> Actually, using gptboot in HEAD you can now boot from GPT on large volumes
> (I've booted from a > 2 TB volume on a PERC5 using mfi(4) with it).  I
> will see about getting that merged back to 6.x and 7.x in CVS.  We use
> it for large volumes on 6.x and all volumes on 7.x at work.
>
> > When I said there was nothing relevant waiting for MFC, I was aware of
> > the change that Tom mentioned, but that seems to be about Dell PERC 6
> > being identified as such rather than a MegaRAID. It doesn't seem that it
> > will change the behaviour of the driver in any way.
>
> In our testing at work the 2950 rev 3's worked fine with mfi(4).
>
> --
> John Baldwin
>

Hi John,

Nice to hear that.

Regards,
Aldas