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Date:      Tue, 19 Jul 2011 11:52:18 -0700
From:      Chuck Swiger <cswiger@mac.com>
To:        tomdean@speakeasy.org
Cc:        "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org>
Subject:   Re: Install 8.2-Release AMD64 on Laptop with Raid0
Message-ID:  <9D63F24F-6A44-4BF5-8DB9-969CDE8236AB@mac.com>
In-Reply-To: <1311100273.2262.22.camel@asus>
References:  <1311099631.2262.20.camel@asus> <D0052936-F387-4B16-BE63-9B5D12178AFF@mac.com> <1311100273.2262.22.camel@asus>

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On Jul 19, 2011, at 11:31 AM, Thomas D. Dean wrote:
>> ar0 is the RAID-0 volume.  However, I would advise against using Intel's Matrix pseudo-RAID for a boot volume, 
> 
> Why?
> 
> I searched and did not find a reason to not use it.  Just a few
> "recommend against it" without reasons.

There's a set of FreeBSD PR's mentioned at the bottom of:

  http://en.wikipedia.org/wiki/Intel_Matrix_RAID

If you lost a disk even when using mirroring, the system would likely panic and experience data corruption.  If you had a disk drop off and reattach, it would possibly be probed as a different RAID volume.

There have been some recent fixes to GEOM RAID mentioned below which are relevant.

Regards,
-- 
-Chuck

Begin forwarded message:
> From: Jeremy Chadwick <freebsd@jdc.parodius.com>
> Date: June 17, 2011 5:51:24 PM PDT
> To: freebsd-stable@freebsd.org
> Cc: freebsd-fs@freebsd.org
> Subject: MFC: graid(8) (RAID GEOM) support
> 
> Sorry for the cross-post, but I thought both lists would want to know
> about this.
> 
> Looks like mav@ just committed this ~17 hours ago:
> http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/geom/raid/g_raid.c
> 
> Those who have historically wanted to use Intel MatrixRAID (now called
> Intel RST (Rapid Storage Technology)), but haven't due to the severe
> issues/risks with ataraid(4), will probably be very interested in
> this commit.  I know I am!
> 
> I plan on stress-testing the Intel support on a 2-disk system with
> RAID-1 enabled, and will document my experiences, procedures, etc...
> 
> Thanks, mav@ and imp@ !
> 
> I'll be sending another mail momentarily asking about USB memory stick
> image building, since to accomplish the above, I want to do a
> "bare-bones" install on our test system (e.g. enable Intel RAID, set up
> 2 disks in a RAID-1 mirror, boot a USB memory stick that contains this
> latest RELENG_8 build, and do sysinstall, etc.. the normal way).
> 
> 
> =====================================================================
> MFC r219974, r220209, r220210, r220790:
> Add new RAID GEOM class, that is going to replace ataraid(4) in supporting
> various BIOS-based software RAIDs. Unlike ataraid(4) this implementation
> does not depend on legacy ata(4) subsystem and can be used with any disk
> drivers, including new CAM-based ones (ahci(4), siis(4), mvs(4), ata(4)
> with `options ATA_CAM`). To make code more readable and extensible, this
> implementation follows modular design, including core part and two sets
> of modules, implementing support for different metadata formats and RAID
> levels.
> 
> Support for such popular metadata formats is now implemented:
> Intel, JMicron, NVIDIA, Promise (also used by AMD/ATI) and SiliconImage.
> 
> Such RAID levels are now supported:
> RAID0, RAID1, RAID1E, RAID10, SINGLE, CONCAT.
> 
> For all of these RAID levels and metadata formats this class supports
> full cycle of volume operations: reading, writing, creation, deletion,
> disk removal and insertion, rebuilding, dirty shutdown detection
> and resynchronization, bad sector recovery, faulty disks tracking,
> hot-spare disks. For Intel and Promise formats there is support multiple
> volumes per disk set.
> 
> Look graid(8) manual page for additional details.
> 
> Co-authored by: imp
> Sponsored by:   Cisco Systems, Inc. and iXsystems, Inc.
> =====================================================================
> 
> -- 
> | Jeremy Chadwick                                jdc at parodius.com |
> | Parodius Networking                       http://www.parodius.com/ |
> | UNIX Systems Administrator                   Mountain View, CA, US |
> | Making life hard for others since 1977.               PGP 4BD6C0CB |
> 
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