Booting off of RAID10 versus RAID1

Booting off of RAID10 versus RAID1

[Maurice Hilarius]

After recent issues discovered with RAID1 and failing disks, I am 
contemplating alternatives to ensure more reliability.

The question that arises: Is there any way to boot a system from a 
RAID10 md?


-- 
Regards, Maurice

Re: Booting off of RAID10 versus RAID1

[Andrew Farley]

I'm pretty sure you can't put the kernel on a raid 10, but you can  
have a 50-100MB RAID1 (or not raid) /boot partition (on each hdd if  
you wish) and then have root on raid 10 provided you compile in  
support for it or use a initrd.  I have used this setup successfully  
without the kernel raid 10 support (older linux distro).  I just have  
a raid 0 on top of three raid 1's that auto assemble the raid 1's upon  
boot but then have to manually assemble the raid 0 since the boot-up  
procedure only does one round of raid auto-detecting.

Just required this little hack in menu.lst

title  Default kernel - build2
root (hd0,0)
kernel /kernel-build2 root=/dev/md4 md=4,/dev/md1,/dev/md2,/dev/md3

Just a trick I used, makes some great vm and/or db servers.  Cheers,

  - A

On May 8, 2008, at 3:34 PM, Maurice Hilarius wrote:

> After recent issues discovered with RAID1 and failing disks, I am  
> contemplating alternatives to ensure more reliability.
>
> The question that arises: Is there any way to boot a system from a  
> RAID10 md?

Re: Booting off of RAID10 versus RAID1

[Keld Jørn Simonsen]

On Thu, May 08, 2008 at 07:34:12AM -0600, Maurice Hilarius wrote:
> After recent issues discovered with RAID1 and failing disks, I am 
> contemplating alternatives to ensure more reliability.
> 
> The question that arises: Is there any way to boot a system from a 
> RAID10 md?

I believe you can boot off a raid10,n2 array.

best regards
keld

Re: Booting off of RAID10 versus RAID1

[David Greaves]

Maurice Hilarius wrote:
> After recent issues discovered with RAID1 and failing disks, I am
> contemplating alternatives to ensure more reliability.
> 
> The question that arises: Is there any way to boot a system from a
> RAID10 md?

I've been wondering about booting grub/initrd from a flash USB stick (industrial
quality if needed).

David

Re: Booting off of RAID10 versus RAID1

[David Lethe]

I know of several vendors that have linux-based NAS appliance vendors who do this. It is rock solid, as long as you don't use consumer-quality usb flash.  Check specs on flash memory for throughput and write cycles and ECC and choose accordingly. Also look into IDE mounted flash. It directly plugs into IDE plug on mobo, so it will be internal, and emulates an ide disk.  

-----Original Message-----

From:  "David Greaves" <david@dgreaves.com>
Subj:  Re: Booting off of RAID10 versus RAID1
Date:  Thu May 8, 2008 10:31 am
Size:  556 bytes
To:  "Maurice Hilarius" <maurice@harddata.com>
cc:  "linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>

Maurice Hilarius wrote: 
> After recent issues discovered with RAID1 and failing disks, I am 
> contemplating alternatives to ensure more reliability. 
>  
> The question that arises: Is there any way to boot a system from a 
> RAID10 md? 
 
I've been wondering about booting grub/initrd from a flash USB stick (industrial 
quality if needed). 
 
David 
 
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Re: Booting off of RAID10 versus RAID1

[Twigathy]

My desktop NFS boots off my fileserver, with a local /boot partition
on a 2GB CompactFlash card in an IDE -> CF adapter bought for pennies
on fleabay. With a partition like /boot that doesn't get written to
very often (Only on kernel updates and initrd changes) I don't see the
write limitations as being too much of a problem. Not sure how well
they would fare in a raid1 setup, but again they'd only be written to
occasionally.

2008/5/8 David Lethe <david@santools.com>:
> I know of several vendors that have linux-based NAS appliance vendors who do this. It is rock solid, as long as you don't use consumer-quality usb flash.  Check specs on flash memory for throughput and write cycles and ECC and choose accordingly. Also look into IDE mounted flash. It directly plugs into IDE plug on mobo, so it will be internal, and emulates an ide disk.
>
>
>
>  -----Original Message-----
>
>  From:  "David Greaves" <david@dgreaves.com>
>  Subj:  Re: Booting off of RAID10 versus RAID1
>  Date:  Thu May 8, 2008 10:31 am
>  Size:  556 bytes
>  To:  "Maurice Hilarius" <maurice@harddata.com>
>  cc:  "linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>
>
>  Maurice Hilarius wrote:
>  > After recent issues discovered with RAID1 and failing disks, I am
>  > contemplating alternatives to ensure more reliability.
>  >
>  > The question that arises: Is there any way to boot a system from a
>  > RAID10 md?
>
>  I've been wondering about booting grub/initrd from a flash USB stick (industrial
>  quality if needed).
>
>  David
>
>  --
>  To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>  the body of a message to majordomo@vger.kernel.org
>  More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>
>  --
>  To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>  the body of a message to majordomo@vger.kernel.org
>  More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: Booting off of RAID10 versus RAID1

[Tomasz Chmielewski]

Twigathy schrieb:
> My desktop NFS boots off my fileserver, with a local /boot partition
> on a 2GB CompactFlash card in an IDE -> CF adapter bought for pennies
> on fleabay. With a partition like /boot that doesn't get written to
> very often (Only on kernel updates and initrd changes) I don't see the
> write limitations as being too much of a problem. Not sure how well
> they would fare in a raid1 setup, but again they'd only be written to
> occasionally.

For my SAN servers, I usually have a system installed on a IDE-flash or a 
USB-stick; data is stored separately on hard disks.

This way, an operating system is independent of data - in case of any operating 
system failure, just replace a small flash module, and you have access to data 
again. Having an operating system together with data on any RAID makes recovery 
from failures much harder.

Of course, everything depends on your usage.


So far, I had only one problem with worn out flash: I placed RAID bitmap on 
flash, and some time later, I had I/O errors when trying to access the bitmap 
file. Probably Transcend IDE-flash disks don't do a very clever wear-levelling.

Other than that, I don't have any problems - although some of these systems run 
off flash for several years now (including /var/log/).

See also a recent "Compact Flash Question" discussion on lkml.


-- 
Tomasz Chmielewski
http://wpkg.org

Re: Booting off of RAID10 versus RAID1

[Bill Davidsen]

David Greaves wrote:
> Maurice Hilarius wrote:
>   
>> After recent issues discovered with RAID1 and failing disks, I am
>> contemplating alternatives to ensure more reliability.
>>
>> The question that arises: Is there any way to boot a system from a
>> RAID10 md?
>>     
>
> I've been wondering about booting grub/initrd from a flash USB stick (industrial
> quality if needed).
>   

Not needed, you won't be writing it often (I hope!), so just the MBR and 
/boot can go on that device.

-- 
Bill Davidsen <davidsen@tmr.com>
  "Woe unto the statesman who makes war without a reason that will still
  be valid when the war is over..." Otto von Bismark 

Re: Booting off of RAID10 versus RAID1

[Keld Jørn Simonsen]

On Thu, May 08, 2008 at 04:40:16PM +0200, Keld Jørn Simonsen wrote:
> On Thu, May 08, 2008 at 07:34:12AM -0600, Maurice Hilarius wrote:
> > After recent issues discovered with RAID1 and failing disks, I am 
> > contemplating alternatives to ensure more reliability.
> > 
> > The question that arises: Is there any way to boot a system from a 
> > RAID10 md?
> 
> I believe you can boot off a raid10,n2 array.

You should also be able to boot off a raid5 array with 2 disks!

Best regards
keld
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