Re: Partition or whole disk ?

Re: Partition or whole disk ?

[Ryan B. Lynch]

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On Wednesday 30 June 2004 02:55 pm, Jan-Benedict Glaw wrote:
> On Wed, 2004-06-30 10:15:41 -0400, Josh Litherland <josh@emperorlinux.com>

> I can't remember any recommendation being spoken out ever. Personally, I
> prefer having a number of partitions, but that's not a general guide for
> everybody else:)
>
> > Is there any functional reason why either one is better ?

Isn't it true that autodetection won't work if you build it out of whole 
disks, though?  The kernel looks for "fd" type partitions to add to RAID 
arrays on boot and sets them up according to their superblocks.  An array 
made of whole-disks couldn't have partition types, so it couldn't use this to 
setup.

This is my understanding, so if I'm wrong, please let me know.

- -Ryan
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Partition or whole disk ?

[Josh Litherland]

Couldn't find an authoritative answer to this in the faq or elsewhere...
Is it preferred to build md sets out of whole disks or of partitions ? 
Is there any functional reason why either one is better ?

-- 
Josh Litherland <josh@emperorlinux.com>
Emperor Linux

Re: Partition or whole disk ?

[Jan-Benedict Glaw]

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On Wed, 2004-06-30 10:15:41 -0400, Josh Litherland <josh@emperorlinux.com>
wrote in message <1088604941.2840.1.camel@JubJub>:
> 
> Couldn't find an authoritative answer to this in the faq or elsewhere...

Use either one of those.

> Is it preferred to build md sets out of whole disks or of partitions ? 

I can't remember any recommendation being spoken out ever. Personally, I
prefer having a number of partitions, but that's not a general guide for
everybody else:)

> Is there any functional reason why either one is better ?

Not really... You loose a few KBs or MBs if you use partitions, but
that's it...

MfG, JBG

-- 
   Jan-Benedict Glaw       jbglaw@lug-owl.de    . +49-172-7608481
   "Eine Freie Meinung in  einem Freien Kopf    | Gegen Zensur | Gegen Krieg
    fuer einen Freien Staat voll Freier Bürger" | im Internet! |   im Irak!
   ret = do_actions((curr | FREE_SPEECH) & ~(NEW_COPYRIGHT_LAW | DRM | TCPA));

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RE: Partition or whole disk ?

[Guy]

A partition of type FD is required to autodetect the array(s).

Guy

-----Original Message-----
From: linux-raid-owner@vger.kernel.org
[mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Jan-Benedict Glaw
Sent: Wednesday, June 30, 2004 10:56 AM
To: linux-raid@vger.kernel.org
Subject: Re: Partition or whole disk ?

On Wed, 2004-06-30 10:15:41 -0400, Josh Litherland <josh@emperorlinux.com>
wrote in message <1088604941.2840.1.camel@JubJub>:
> 
> Couldn't find an authoritative answer to this in the faq or elsewhere...

Use either one of those.

> Is it preferred to build md sets out of whole disks or of partitions ? 

I can't remember any recommendation being spoken out ever. Personally, I
prefer having a number of partitions, but that's not a general guide for
everybody else:)

> Is there any functional reason why either one is better ?

Not really... You loose a few KBs or MBs if you use partitions, but
that's it...

MfG, JBG

-- 
   Jan-Benedict Glaw       jbglaw@lug-owl.de    . +49-172-7608481
   "Eine Freie Meinung in  einem Freien Kopf    | Gegen Zensur | Gegen Krieg
    fuer einen Freien Staat voll Freier Bürger" | im Internet! |   im Irak!
   ret = do_actions((curr | FREE_SPEECH) & ~(NEW_COPYRIGHT_LAW | DRM |
TCPA));

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Re: Partition or whole disk ?

[Dieter Stueken]

Josh Litherland wrote:
> Couldn't find an authoritative answer to this in the faq or elsewhere...
> Is it preferred to build md sets out of whole disks or of partitions ? 
> Is there any functional reason why either one is better ?

If you make partitions, about one track is is "wasted" to store
the useless partition table. Thus I used whole disks for a long time.

The problem might be, that "fdisk -l" won't show up if this
disk is an MD device. It shows an empty partition table which
may look like an unused/empty disk. If you create the partition
table, you may waste some data, but fdisk may show this is a
disk with a partition containing some MD data on it.

Meanwhile I turned back to make partition tables again,
just to "tag" the disk as "in use". If I put a new disk
into my system, it has no partition table. Thus I can verify
this condition, before I initialize the disk. This may prevent
me from accidentally initialize/destroying some disk in use,
which already has an partition table.

Dieter.

Re: Partition or whole disk ?

[Mark Hahn]

> Couldn't find an authoritative answer to this in the faq or elsewhere...
> Is it preferred to build md sets out of whole disks or of partitions ? 
> Is there any functional reason why either one is better ?

as others have pointed out, there's little reason (save a track
on whole-disk, lose partition-type-0xfd auto-detection).

however, if you go the partition route, don't go too far!
I've seen several cases where someone gets overly enthusiastic
about multiple parallel raids across a small set of disks.
they wind up shuffling the heads between partitions for an 
obscene fraction of time.  this can be especially noticable 
with journalling filesystems, since they tend to do synchronous
log forces on a regular basis.  don't even get me started on 
people who set their mail spools to pure-sync!  (hmm, why can 
my awesome new quad-opteron mail server only receive 10 email/sec?)