[gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Wolfgang Liebich]

Hi,
I'm in the process of setting up a new private computer. I've bought one
with two drives b/c I wanted to setup a RAID system - RAID1 for
important partitions, RAID0 for scratch files maybe.
Additionally I would like to use LVM2 --- on my work PC I've grown to
like the flexibility of that.
The Intel DQ35JO motherboard now supports some kind of mobo based RAID.
Is it better to use this HW raid, or to ignore that and use only the
linux kernel's software RAID.
Additionally the LVM2 utilities seem to have limited mirroring/striping
capabilities of their own - I only want to use RAID levels 0 and 1
anyways -- would LVM's methods be better here?

Inquiring mind wants to know!
- Wolfgang Liebich

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Pintér Tibor]

> I'm in the process of setting up a new private computer. I've bought one
> with two drives b/c I wanted to setup a RAID system - RAID1 for
> important partitions, RAID0 for scratch files maybe.
> Additionally I would like to use LVM2 --- on my work PC I've grown to
> like the flexibility of that.
> The Intel DQ35JO motherboard now supports some kind of mobo based RAID.
> Is it better to use this HW raid, or to ignore that and use only the
> linux kernel's software RAID.

thats not hardware raid, it never was, it never will be.

t

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Alan McKinnon]

On Wednesday 15 October 2008 15:13:45 Pintér Tibor wrote:
> > I'm in the process of setting up a new private computer. I've bought one
> > with two drives b/c I wanted to setup a RAID system - RAID1 for
> > important partitions, RAID0 for scratch files maybe.
> > Additionally I would like to use LVM2 --- on my work PC I've grown to
> > like the flexibility of that.
> > The Intel DQ35JO motherboard now supports some kind of mobo based RAID.
> > Is it better to use this HW raid, or to ignore that and use only the
> > linux kernel's software RAID.
>
> thats not hardware raid, it never was, it never will be.

Rule of thumb:

For any machine you buy to use at home, dump the on-board RAID and use Linux 
software raid instead.

Reason: kernel raid works, that on-board crap doesn't
Other reason: real hardware raid costs many times more than that entire 
computer you bought for home use


-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Dirk Heinrichs]

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Hi,

since you seem to be german, there's an article about SW-/MoBo-/HW-RAID in the 
current issue of c't magazine.

Bye...

	Dirk
-- 
Dirk Heinrichs          | Tel:  +49 (0)162 234 3408
Configuration Manager   | Fax:  +49 (0)211 47068 111
Capgemini Deutschland   | Mail: dirk.heinrichs@capgemini.com
Wanheimerstraße 68      | Web:  http://www.capgemini.com
D-40468 Düsseldorf      | ICQ#: 110037733
GPG Public Key C2E467BB | Keyserver: wwwkeys.pgp.net


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Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Albert Hopkins]

Your mobo RAID is most likely software/BIOS RAID (what some people call
"fake" RAID).  The point is it's software that's doing the real work.

If you want to be sure your data is still readable in the event that
your mobo dies and you can't find a replacement with the same "fake"
RAID controller, stick with Linux kernel RAID.

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Pintér Tibor]

> If you want to be sure your data is still readable in the event that
> your mobo dies and you can't find a replacement with the same "fake"
> RAID controller, stick with Linux kernel RAID.

...or buy a 3ware/areca/adaptec card, which is 100% supported.
(but those are heavy bucks)

t

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Dan Cowsill]

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Hi guys,

I've had some experience in the past with software (BIOS) RAID. 
Obviously there would be a big performance difference with hardware vs
BIOS RAID.  Has anyone done any benchmarks to the effect of BIOS vs
linux kernel RAID?

Thanks,
D

Wolfgang Liebich wrote:
> Hi,
> I'm in the process of setting up a new private computer. I've bought one
> with two drives b/c I wanted to setup a RAID system - RAID1 for
> important partitions, RAID0 for scratch files maybe.
> Additionally I would like to use LVM2 --- on my work PC I've grown to
> like the flexibility of that.
> The Intel DQ35JO motherboard now supports some kind of mobo based RAID.
> Is it better to use this HW raid, or to ignore that and use only the
> linux kernel's software RAID.
> Additionally the LVM2 utilities seem to have limited mirroring/striping
> capabilities of their own - I only want to use RAID levels 0 and 1
> anyways -- would LVM's methods be better here?
>
> Inquiring mind wants to know!
> - Wolfgang Liebich
>
>   



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Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Volker Armin Hemmann]

On Mittwoch 15 Oktober 2008, Dan Cowsill wrote:
> Hi guys,
>
> I've had some experience in the past with software (BIOS) RAID.
> Obviously there would be a big performance difference with hardware vs
> BIOS RAID.  Has anyone done any benchmarks to the effect of BIOS vs
> linux kernel RAID?

yes. google for it. linux software always wins. Faster, more flexible.

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Paul Hartman]

On Wed, Oct 15, 2008 at 8:08 AM, Wolfgang Liebich
<wolfgang.liebich@siemens.com> wrote:
> Hi,
> I'm in the process of setting up a new private computer. I've bought one
> with two drives b/c I wanted to setup a RAID system - RAID1 for
> important partitions, RAID0 for scratch files maybe.
> Additionally I would like to use LVM2 --- on my work PC I've grown to
> like the flexibility of that.
> The Intel DQ35JO motherboard now supports some kind of mobo based RAID.
> Is it better to use this HW raid, or to ignore that and use only the
> linux kernel's software RAID.
> Additionally the LVM2 utilities seem to have limited mirroring/striping
> capabilities of their own - I only want to use RAID levels 0 and 1
> anyways -- would LVM's methods be better here?

Hi,

I've got 4 regular 500gb SATA drives in a linux software RAID5 (BIOS
fakeraid disabled), not using LVM, and with a AES dmcrypt on top of
it, and the performance is really good in my opinion. The encrypted
RAID has a faster read speed than a single, non-RAID, non-encrypted
SATA drive of the same model. Obviously with the encryption & parity
calculations the writes are not as fast, but it's still 25 megabytes
per second write speed which seems pretty good to me. I have a Core 2
E6600 (overclocked to 3ghz).

The time to rebuild the RAID after a system failure for this 4x500gb
is about 90 minutes.

Good luck,
Paul

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Wolfgang Liebich]

Hi,

Alan McKinnon schrieb:
> On Wednesday 15 October 2008 15:13:45 Pintér Tibor wrote:
>   
>>> I'm in the process of setting up a new private computer. I've bought one
>>> with two drives b/c I wanted to setup a RAID system - RAID1 for
>>> important partitions, RAID0 for scratch files maybe.
>>> Additionally I would like to use LVM2 --- on my work PC I've grown to
>>> like the flexibility of that.
>>> The Intel DQ35JO motherboard now supports some kind of mobo based RAID.
>>> Is it better to use this HW raid, or to ignore that and use only the
>>> linux kernel's software RAID.
>>>       
>> thats not hardware raid, it never was, it never will be.
>>     
>
> Rule of thumb:
>
> For any machine you buy to use at home, dump the on-board RAID and use Linux 
> software raid instead.
>
> Reason: kernel raid works, that on-board crap doesn't
> Other reason: real hardware raid costs many times more than that entire 
> computer you bought for home use
>
>   
OK - nearly everyone here (and at work, too) told me to forget the
onboard fake raid controller. So this is what I will do :-)
The RAID-Howto as well as the LVM howto are however woefully out of
date. I will try to work with the linux-raid website's info.

Basically I plan to do:
- Put the boot partition on a RAID1
- Put the root partition on another RAID1 (I thought about putting the
root filesystem into my LVM setup, too -- it is REALLY annoying if the
root partition get's to small),
  but it seems safer to let root be an own partition. Or are there any
different opinions here? I'm very interested in hearing experiences...
- Build a RAID1 partition for the rest of the system (will be a LVM2
container)
- Build a last RAID0 partition for scratch data (/tmp, /var/tmp,
/usr/portage, scratch data).

Any comments? Obviously insane? :-) Don't think so.
- Wolfgang

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Neil Bothwick]

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On Fri, 17 Oct 2008 12:40:52 +0200, Wolfgang Liebich wrote:

> Basically I plan to do:
> - Put the boot partition on a RAID1
> - Put the root partition on another RAID1 (I thought about putting the
> root filesystem into my LVM setup, too -- it is REALLY annoying if the
> root partition get's to small),
>   but it seems safer to let root be an own partition. Or are there any
> different opinions here? I'm very interested in hearing experiences...

I have a small root partition on RAID1 and everything else (except swap)
in an LVM group, also on RAID. This avoids the need for a separate /boot.


-- 
Neil Bothwick

Isn't 'Criminal Lawyer' rather redundant?

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Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Volker Armin Hemmann]

On Freitag 17 Oktober 2008, Wolfgang Liebich wrote:
> Hi,
>
> Alan McKinnon schrieb:
> > On Wednesday 15 October 2008 15:13:45 Pintér Tibor wrote:
> >>> I'm in the process of setting up a new private computer. I've bought
> >>> one with two drives b/c I wanted to setup a RAID system - RAID1 for
> >>> important partitions, RAID0 for scratch files maybe.
> >>> Additionally I would like to use LVM2 --- on my work PC I've grown to
> >>> like the flexibility of that.
> >>> The Intel DQ35JO motherboard now supports some kind of mobo based RAID.
> >>> Is it better to use this HW raid, or to ignore that and use only the
> >>> linux kernel's software RAID.
> >>
> >> thats not hardware raid, it never was, it never will be.
> >
> > Rule of thumb:
> >
> > For any machine you buy to use at home, dump the on-board RAID and use
> > Linux software raid instead.
> >
> > Reason: kernel raid works, that on-board crap doesn't
> > Other reason: real hardware raid costs many times more than that entire
> > computer you bought for home use
>
> OK - nearly everyone here (and at work, too) told me to forget the
> onboard fake raid controller. So this is what I will do :-)
> The RAID-Howto as well as the LVM howto are however woefully out of
> date. I will try to work with the linux-raid website's info.

the howtos on gentoo-wiki worked well for me.


> - Put the root partition on another RAID1 (I thought about putting the
> root filesystem into my LVM setup, too -- it is REALLY annoying if the
> root partition get's to small),

yeah, but if you have 20+ gb root is always big enough ;) AFAIK lvm kills 
barriers. You use raid for better data security. So using lvm is a bit.. 
contra productive.


> - Build a RAID1 partition for the rest of the system (will be a LVM2
> container)
> - Build a last RAID0 partition for scratch data (/tmp, /var/tmp,
> /usr/portage, scratch data).

I have /tmp and /var/tmp on tmpfs - /tmp is so small it is not worth wasting a 
partition for it.

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[jormaa]

Wolfgang Liebich wrote:
> Hi,
>
>   
> OK - nearly everyone here (and at work, too) told me to forget the
> onboard fake raid controller. So this is what I will do :-)
> The RAID-Howto as well as the LVM howto are however woefully out of
> date. I will try to work with the linux-raid website's info.
>
> Basically I plan to do:
> - Put the boot partition on a RAID1
> - Put the root partition on another RAID1 (I thought about putting the
> root filesystem into my LVM setup, too -- it is REALLY annoying if the
> root partition get's to small),
>   but it seems safer to let root be an own partition. Or are there any
> different opinions here? I'm very interested in hearing experiences...
> - Build a RAID1 partition for the rest of the system (will be a LVM2
> container)
> - Build a last RAID0 partition for scratch data (/tmp, /var/tmp,
> /usr/portage, scratch data).
>
> Any comments? Obviously insane? :-) Don't think so.
> - Wolfgang
>
>
>   
Likewhoa has a nice writedown of raid and LVM2 on gentoo forums
http://forums.gentoo.org/viewtopic-t-702681-highlight-likewhoa+recipe.html?sid=e9df56d90808ed712323ca693936a004.

Using that it should be easy enough to adjust to your needs.

Greets jormaa

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Peter Humphrey]

On Friday 17 October 2008 12:43:15 Volker Armin Hemmann wrote:

> I have /tmp and /var/tmp on tmpfs - /tmp is so small it is not worth
> wasting a partition for it.

Yes, and you can enlarge it by creating plenty of swap. My 4GB of real RAM 
isn't enough to compile the biggest programs, but setting /etc/fstab 
thus: "tmpfs  /tmp  tmpfs  nodev,nosuid,size=6g  0 0" I get enough /tmp 
space when I need it without have to go out and spend money on more RAM. 
Neat.

-- 
Rgds
Peter

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Wolfgang Liebich]

Hi,

<SNIP>
> 
> the howtos on gentoo-wiki worked well for me.

I'm working with them, too. Just one question remains: I want to use
udev. Do I have to create the md devices or does udev that for me?

> 
> 
> > - Put the root partition on another RAID1 (I thought about putting the
> > root filesystem into my LVM setup, too -- it is REALLY annoying if the
> > root partition get's to small),
> 
> yeah, but if you have 20+ gb root is always big enough ;) AFAIK lvm kills 
> barriers. You use raid for better data security. So using lvm is a bit.. 
> contra productive.

Sorry, I'm neither a LVM nor a RAID export - could you please
elaborate on that?
I like LVM because of the convenience it adds.

> 
> 
> > - Build a RAID1 partition for the rest of the system (will be a LVM2
> > container)
> > - Build a last RAID0 partition for scratch data (/tmp, /var/tmp,
> > /usr/portage, scratch data).
> 
> I have /tmp and /var/tmp on tmpfs - /tmp is so small it is not worth wasting a 
> partition for it.

/tmp --- maybe now (4GB ram). /var/tmp - not sure (OpenOffice compile
comes to mind here :-)
Ciao,
Wolfgang

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Conway S. Smith]

On Mon, 20 Oct 2008 08:54:20 +0200
Wolfgang Liebich <Wolfgang.Liebich@siemens.com> wrote:
> Hi,
> 
> <SNIP>
> > 
> > the howtos on gentoo-wiki worked well for me.
> 
> I'm working with them, too. Just one question remains: I want to use
> udev. Do I have to create the md devices or does udev that for me?
> 

udev will do it for you.  But make sure your initramfs init script
unmounts /sys & /proc.  On the box I'm working on setting up it
wasn't unmounting /sys on the initramfs, so when it switched to the
real root it thought /sys was already mounted & didn't mount /sys
under the real root, which meant that udev didn't work - which took
me a while to figure out.

> > 
> > 
> > > - Put the root partition on another RAID1 (I thought about
> > > putting the root filesystem into my LVM setup, too -- it is
> > > REALLY annoying if the root partition get's to small),
> > 
> > yeah, but if you have 20+ gb root is always big enough ;) AFAIK
> > lvm kills barriers. You use raid for better data security. So
> > using lvm is a bit.. contra productive.
> 
> Sorry, I'm neither a LVM nor a RAID export - could you please
> elaborate on that?
> I like LVM because of the convenience it adds.
> 

Write barriers are a feature to allow write caching on the hard disks
w/out endangering filesystem integrity.  Write caching helps
performance significantly, but also allows the disk to re-order write
requests - the disk may actually write a write-request that was
received later before a write-request that was received earlier,
which in some situations can lead to filesystem corruption.  Write
barriers are a special type of request that the disk is not allowed
to reorder around - everything the disk receives before the write
barrier must be written before anything received after the write
barrier.  But in order to work, write barriers need to be supported
by every layer from the filesystem down to the actual disk; if your
filesystem is on top of LVM & LVM doesn't support write barriers,
then you won't be able to use them, and if write caching is enabled
on the actual disks, you may be risking fileystem corruption.  The
Device Mapper kernel subsystem (dm-crypt, dm-raid, LVM, etc.) does
not support write barriers - but neither does MD RAID except for
RAID1, so write caching is dangerous except for filesystems directly
on disk partitions or on RAID1 (if the RAID1 is directly on disk
partitions).

I personally decided against using LVM because from what I read it's
difficult to correctly stripe-align LVM, and incorrect alignment can
have a very big performance impact.


Good luck,
Conway S. Smith
-- 
The only "intuitive" interface is the nipple. After that, it's all
learned. (Bruce Ediger, bediger@teal.csn.org, in comp.os.linux.misc,
on X interfaces.)

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Volker Armin Hemmann]

On Montag 20 Oktober 2008, Conway S. Smith wrote:
> On Mon, 20 Oct 2008 08:54:20 +0200
>
> Wolfgang Liebich <Wolfgang.Liebich@siemens.com> wrote:
> > Hi,
> >
> > <SNIP>
> >
> > > the howtos on gentoo-wiki worked well for me.
> >
> > I'm working with them, too. Just one question remains: I want to use
> > udev. Do I have to create the md devices or does udev that for me?
>
> udev will do it for you.  But make sure your initramfs init script
> unmounts /sys & /proc. 

just don't use an initramfs/initrd.

> > Sorry, I'm neither a LVM nor a RAID export - could you please
> > elaborate on that?
> > I like LVM because of the convenience it adds.
>
> Write barriers are a feature to allow write caching on the hard disks
> w/out endangering filesystem integrity.  Write caching helps
> performance significantly, but also allows the disk to re-order write
> requests - the disk may actually write a write-request that was
> received later before a write-request that was received earlier,
> which in some situations can lead to filesystem corruption.  Write
> barriers are a special type of request that the disk is not allowed
> to reorder around - everything the disk receives before the write
> barrier must be written before anything received after the write
> barrier.  But in order to work, write barriers need to be supported
> by every layer from the filesystem down to the actual disk; if your
> filesystem is on top of LVM & LVM doesn't support write barriers,
> then you won't be able to use them, and if write caching is enabled
> on the actual disks, you may be risking fileystem corruption.  The
> Device Mapper kernel subsystem (dm-crypt, dm-raid, LVM, etc.) does
> not support write barriers - but neither does MD RAID except for
> RAID1, so write caching is dangerous except for filesystems directly
> on disk partitions or on RAID1 (if the RAID1 is directly on disk
> partitions).

also, reiserfs and xfs turn barriers on by default, ext3 turns it off per 
default. Because of 'performance reasons'.

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Conway S. Smith]

On Mon, 20 Oct 2008 13:24:11 +0200
Volker Armin Hemmann <volker.armin.hemmann@tu-clausthal.de> wrote:
> On Montag 20 Oktober 2008, Conway S. Smith wrote:
> > On Mon, 20 Oct 2008 08:54:20 +0200
> >
> > Wolfgang Liebich <Wolfgang.Liebich@siemens.com> wrote:
> > > Hi,
> > >
> > > <SNIP>
> > >
> > > > the howtos on gentoo-wiki worked well for me.
> > >
> > > I'm working with them, too. Just one question remains: I want
> > > to use udev. Do I have to create the md devices or does udev
> > > that for me?
> >
> > udev will do it for you.  But make sure your initramfs init script
> > unmounts /sys & /proc. 
> 
> just don't use an initramfs/initrd.
> 

From my reading initramfs/initrd is the preferred way of handling
root filesystem on MD RAID - and the only way for metadata 1.[012]
(although I'm having trouble finding where I read that only 0.90
works w/ in-kernel detection/assembly).

From /usr/share/doc/mdadm-2.6.7/README.initramfs.bz2: "The preferred
way to assemble md arrays at boot time is using 'mdadm' or
'mdassemble' (which is a trimmed-down mdadm).  To assemble an array
which contains the root filesystem, mdadm needs to be run before that
filesystem is mounted, and so needs to be run from an initial-ram-fs."


Conway S. Smith
-- 
The only "intuitive" interface is the nipple. After that, it's all
learned. (Bruce Ediger, bediger@teal.csn.org, in comp.os.linux.misc,
on X interfaces.)

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Volker Armin Hemmann]

On Montag 20 Oktober 2008, Conway S. Smith wrote:
> On Mon, 20 Oct 2008 13:24:11 +0200
>
> Volker Armin Hemmann <volker.armin.hemmann@tu-clausthal.de> wrote:
> > On Montag 20 Oktober 2008, Conway S. Smith wrote:
> > > On Mon, 20 Oct 2008 08:54:20 +0200
> > >
> > > Wolfgang Liebich <Wolfgang.Liebich@siemens.com> wrote:
> > > > Hi,
> > > >
> > > > <SNIP>
> > > >
> > > > > the howtos on gentoo-wiki worked well for me.
> > > >
> > > > I'm working with them, too. Just one question remains: I want
> > > > to use udev. Do I have to create the md devices or does udev
> > > > that for me?
> > >
> > > udev will do it for you.  But make sure your initramfs init script
> > > unmounts /sys & /proc.
> >
> > just don't use an initramfs/initrd.
>
> From my reading initramfs/initrd is the preferred way of handling
> root filesystem on MD RAID - and the only way for metadata 1.[012]
> (although I'm having trouble finding where I read that only 0.90
> works w/ in-kernel detection/assembly).
>
> From /usr/share/doc/mdadm-2.6.7/README.initramfs.bz2: "The preferred
> way to assemble md arrays at boot time is using 'mdadm' or
> 'mdassemble' (which is a trimmed-down mdadm).  To assemble an array
> which contains the root filesystem, mdadm needs to be run before that
> filesystem is mounted, and so needs to be run from an initial-ram-fs."
>
after a nice person on this list gave me a good tip, I was able to (and I 
still do) have root on raid1 without initrd/ramfs crap.

commandline:
root=/dev/md1 md=1,1,/dev/sda3,/dev/sdb3 nopat nmi_watchdog=0

md auto assembling before init kicks in:
[    4.066796] md: Autodetecting RAID arrays.                                                                
[    4.139083] md: Scanned 8 and added 8 devices.                                                            
[    4.139158] md: autorun ...                                                                               
[    4.139232] md: considering sdb6 ...                                                                      
[    4.139309] md:  adding sdb6 ...                                                                          
[    4.139384] md: sdb5 has different UUID to sdb6                                                           
[    4.139460] md: sdb3 has different UUID to sdb6                                                           
[    4.139535] md: sdb1 has different UUID to sdb6                                                           
[    4.139611] md:  adding sda6 ...                                                                          
[    4.139686] md: sda5 has different UUID to sdb6                                                           
[    4.139761] md: sda3 has different UUID to sdb6                                                           
[    4.139837] md: sda1 has different UUID to sdb6                                                           
[    4.140008] md: created md3                                                                               
[    4.140084] md: bind<sda6>                                                                                
[    4.140162] md: bind<sdb6>                                                                                
[    4.140240] md: running: <sdb6><sda6>                                                                     
[    4.140533] raid1: raid set md3 active with 2 out of 2 mirrors                                            
[    4.140650] md: considering sdb5 ...                                                                      
[    4.140726] md:  adding sdb5 ...                                                                          
[    4.140801] md: sdb3 has different UUID to sdb5                                                           
[    4.140884] md: sdb1 has different UUID to sdb5                                                           
[    4.140960] md:  adding sda5 ...                                                                          
[    4.141034] md: sda3 has different UUID to sdb5                                                           
[    4.141110] md: sda1 has different UUID to sdb5                                                           
[    4.141259] md: created md2                                                                               
[    4.141334] md: bind<sda5>                                                                                
[    4.141413] md: bind<sdb5>                                                                                
[    4.141491] md: running: <sdb5><sda5>                                                                     
[    4.141757] raid1: raid set md2 active with 2 out of 2 mirrors                                            
[    4.141872] md: considering sdb3 ...                                                                      
[    4.141950] md:  adding sdb3 ...                                                                          
[    4.142025] md: sdb1 has different UUID to sdb3                                                           
[    4.142101] md:  adding sda3 ...                                                                          
[    4.142175] md: sda1 has different UUID to sdb3                                                           
[    4.142325] md: created md1                                                                               
[    4.142399] md: bind<sda3>                                                                                
[    4.142476] md: bind<sdb3>                                                                                
[    4.142554] md: running: <sdb3><sda3>                                                                     
[    4.142818] raid1: raid set md1 active with 2 out of 2 mirrors                                            
[    4.142932] md: considering sdb1 ...                                                                      
[    4.143010] md:  adding sdb1 ...                                                                          
[    4.143086] md:  adding sda1 ...                                                                          
[    4.143160] md: created md0                                                                               
[    4.143234] md: bind<sda1>                                                                                
[    4.143315] md: bind<sdb1>                                                                                
[    4.143400] md: running: <sdb1><sda1>                                                                     
[    4.143666] raid1: raid set md0 active with 2 out of 2 mirrors                                            
[    4.143779] md: ... autorun DONE.                                                                         
[    4.143876] md: Loading md1: 1                                                                            
[    4.143958] md: couldn't update array info. -22                                                           
[    4.144071] md: could not open unknown-block(0,1).                                                        
[    4.144147] md: md_import_device returned -6                                                              
[    4.144230] md: could not bd_claim sda3.                                                                  
[    4.144305] md: md_import_device returned -16                                                             
[    4.144382] md: could not bd_claim sdb3.                                                                  
[    4.144457] md: md_import_device returned -16                                                             
[    4.144533] md: starting md1 failed                                                                       
[    4.189731] reiser4: md1: found disk format 4.0.0.                                                        
[    6.456886] VFS: Mounted root (reiser4 filesystem) readonly.                                              
[    6.456975] Freeing unused kernel memory: 316k freed    

I know what man mdadm says - that initrd is prefered because it is more 
'flexible' - but I prefer not using an initrd because I don't need that crap 
and I really don't want to waste another 2 seconds of boot time on it. 

Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Peter Humphrey]

On Monday 20 October 2008 16:33:24 Volker Armin Hemmann wrote:

> after a nice person on this list gave me a good tip, I was able to (and I
> still do) have root on raid1 without initrd/ramfs crap.
>
> commandline:
> root=/dev/md1 md=1,1,/dev/sda3,/dev/sdb3 nopat nmi_watchdog=0
>
> md auto assembling before init kicks in:

[...]

I don't even need that detail in my command line. (This box has five RAID-1 
partitions, composed of identical partitions on identical SATA disks.) Mine 
just looks like this:

kernel /boot/kernel-x86_64-2.6.27-gentoo root=/dev/md0 vga=0x31A 
video=vesafb:mtrr:3,ywrap fbcon=scrollback:128k splash=silent

The md code in the kernel manages to find all the partitions at boot time 
and stitches them together properly. No problem.

-- 
Rgds
Peter

RE: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Liebich, Wolfgang]

On Mon, 20 Oct 2008 13:24:11 +0200
Volker Armin Hemmann <volker.armin.hemmann@tu-clausthal.de> wrote:
> On Montag 20 Oktober 2008, Conway S. Smith wrote:
> > On Mon, 20 Oct 2008 08:54:20 +0200
> >
> > Wolfgang Liebich <Wolfgang.Liebich@siemens.com> wrote:
> > > Hi,
> > >
> > > <SNIP>
> > >
> > > > the howtos on gentoo-wiki worked well for me.
> > >
> > > I'm working with them, too. Just one question remains: I want
> > > to use udev. Do I have to create the md devices or does udev
> > > that for me?
> >
> > udev will do it for you.  But make sure your initramfs init script
> > unmounts /sys & /proc. 
> 
> just don't use an initramfs/initrd.
> 

From my reading initramfs/initrd is the preferred way of handling
root filesystem on MD RAID - and the only way for metadata 1.[012]
(although I'm having trouble finding where I read that only 0.90
works w/ in-kernel detection/assembly).

From /usr/share/doc/mdadm-2.6.7/README.initramfs.bz2: "The preferred
way to assemble md arrays at boot time is using 'mdadm' or
'mdassemble' (which is a trimmed-down mdadm).  To assemble an array
which contains the root filesystem, mdadm needs to be run before that
filesystem is mounted, and so needs to be run from an initial-ram-fs."


Conway S. Smith
-- 
The only "intuitive" interface is the nipple. After that, it's all
learned. (Bruce Ediger, bediger@teal.csn.org, in comp.os.linux.misc,
on X interfaces.)

AW: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?

[Liebich, Wolfgang]

Hi,




Von: Dirk Heinrichs [mailto:dirk.heinrichs.ext@nsn.com]
 
>Hi,

>since you seem to be german, there's an article about SW-/MoBo-/HW-RAID in the 
>current issue of c't magazine.

Thank you, bought the issue - it was rather helpful to me!
Ciao,
Wolfgang