Whole drives or Only partitions for mdadm software RAIDs?

Hi all,

I have a simple question:

Is there any problem using the full hard drive (/dev/sdb, /dev/sdc,
etc) as opposed to partitions (/dev/sdb1, /dev/sdc1, etc) when creating
software RAIDs? I'd rather commit the full device to the RAID since I
am certain I won't use it for anything else, and I am scripting this so
I don't want to have to fdisk every drive before creating a RAID...that
would take far too much time. Most mdadm documentation always refers to
partitions rather than full devices, so I wanted to make sure it was
indeed OK to use full devices.

Please let me know. Thank you all!

Thanks!
Thomas
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Re: Whole drives or Only partitions for mdadm software RAIDs?

On Mon, 30 Jun 2008, thomas62186218@aol.com wrote:

> Hi all,
>
> I have a simple question:
>
> Is there any problem using the full hard drive (/dev/sdb, /dev/sdc, etc) as
> opposed to partitions (/dev/sdb1, /dev/sdc1, etc) when creating software
> RAIDs? I'd rather commit the full device to the RAID since I am certain I
> won't use it for anything else, and I am scripting this so I don't want to
> have to fdisk every drive before creating a RAID...that would take far too
> much time. Most mdadm documentation always refers to partitions rather than
> full devices, so I wanted to make sure it was indeed OK to use full devices.
>
> Please let me know. Thank you all!
>
> Thanks!
> Thomas
> --
> 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
>

Best to use partitions, so if you over-write the MBR of the drive it
won't mess up the RAID (e.g., run LILO on a raid volume => oops! but if
its a partition, no problems)..

Justin.
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Re: Whole drives or Only partitions for mdadm software RAIDs?

Thanks Justin. If that's the only risk, I'll go with full devices. This=
=20
will ultimately be a headless system with a separate boot drive and=20
only administered by me and used internally, so I'll be careful. :-)

Many thanks!
-Thomas

-----Original Message-----
=46rom: Justin Piszcz
To: thomas62186218@aol.com
Cc: linux-raid@vger.kernel.org
Sent: Mon, 30 Jun 2008 12:50 pm
Subject: Re: Whole drives or Only partitions for mdadm software RAIDs?









 

On Mon, 30 Jun 2008, thomas62186218@aol.com wrote: 
 

> Hi all, 

> 

> I have a simple question: 

> 

> Is there any problem using the full hard drive (/dev/sdb, /dev/sdc,=20
etc) as
> opposed to partitions (/dev/sdb1, /dev/sdc1, etc) when creating=20
software
> RAIDs? I'd rather commit the full device to the RAID since I am=20
certain I
> won't use it for anything else, and I am scripting this so I don't=20
want to
> have to fdisk every drive before creating a RAID...that would take=20
far too
> much time. Most mdadm documentation always refers to partitions=20
rather than
> full devices, so I wanted to make sure it was indeed OK to use full=20
devices. 

> 

> Please let me know. Thank you all! 

> 

> Thanks! 

> Thomas 

> -- 

> To unsubscribe from this list: send the line "unsubscribe linux-raid"=
=20
in 

> the body of a message to majordomo@vger.kernel.org 

> More majordomo info at http://vger.kernel.org/majordomo-info.html=C2=
=A0

> 
 

Best to use partitions, so if you over-write the MBR of the drive it
won't mess up the RAID (e.g., run LILO on a raid volume =3D> oops! but =
if
its a partition, no problems).. 
 

Justin. 

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To unsubscribe from this list: send the line "unsubscribe linux-raid"=20
in 

the body of a message to majordomo@vger.kernel.org 

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Re: Whole drives or Only partitions for mdadm software RAIDs?

Also, if you ever replace a drive there is a distinct chance that the drive will
be a different size (even if it is the same model).

After being bitten by this I always make partition a few Mb smaller than the device.

David

thomas62186218@aol.com wrote:
>
> Thanks Justin. If that's the only risk, I'll go with full devices. This
> will ultimately be a headless system with a separate boot drive and only
> administered by me and used internally, so I'll be careful. :-)
>
> Many thanks!
> -Thomas

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Re: Whole drives or Only partitions for mdadm software RAIDs?

On Tue, July 1, 2008 6:14 am, David Greaves wrote:
> Also, if you ever replace a drive there is a distinct chance that the
> drive will
> be a different size (even if it is the same model).
>
> After being bitten by this I always make partition a few Mb smaller than
> the device.

If you are concerned by this (and it is a valid concern) then you can still
use the whole device, and give the --size option to mdadm --create to
tell it to use a little bit less than the whole device.
You give a size in kilobytes (I really should change that to
accept M or G suffixes I guess).

Personally, I prefer to use whole devices.

NeilBrown


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