Re: Any pros or cons of using full disk versus partitons?

[NeilBrown <neilb@suse.de>]

On Thu, 14 Apr 2011 11:57:47 +0400 CoolCold <coolthecold@gmail.com> wrote:

> On Thu, Apr 14, 2011 at 12:55 AM, David Brown <david.brown@hesbynett.no> wrote:
> > On 13/04/11 22:21, David Miller wrote:
> >>
> >> From: "Matthew Tice"<mjtice@gmail.com>
> >> Date: Wed, 13 Apr 2011 13:38:39 -0600
> >>
> >>> So of course it technically doesn't matter but are there certain
> >>> (non-apparent) repercussions for choosing one over the other?  It seems
> >>> to
> >>> save a couple steps by using the whole disk (not having to partition) -
> >>> but
> >>> is that it?  One thing I'm thinking about the pros of using partitions is
> >>> if
> >>> all your disks (or some) are different sizes - then you can set the
> >>> partition sizes the same.
> >>
> >> First, you sent this to "linux-raid-owner" instead of just
> >> "linux-raid".  The former goes to me, not to the mailing list.
> >>
> >> I've corrected it in the CC:
> >>
> >> Second, to answer your question, for some disk label variants you
> >> risk over-writing the disk label if you use the whole device
> >> as part of your RAID volume.  This definitely will happen, for
> >> example, with Sun disk labels.
> >
> > Using whole disks in the raid will make it easier for replacing disks - you
> > don't have to worry about partitioning them.  You can just plug them in and
> > use them.  If you have some sort of monitoring scripts and hot plug disks,
> > you may be able to avoid any interaction at all on disk replacement.
> >
> > On the other hand, using partitions gives you lots more flexibility. You can
> > do things such as use a small partition on each disk to form a raid10 array
> > for swap, while using a bigger partition for data.  Or perhaps you want a
> > very small partition on each disk as a wide raid1 mirror, for your /boot
> > (not that you need so much safety for /boot, but that it's easier to boot
> > from a raid1 with metadata format 0.90 than from other raid types).
> Just my 2 cents: I've faced problems when newer disk was smaller than
> old disk two or three times, so using partitions now with setting some
> free space at the end - something near 80 or 100 megabytes.

You don't need partitions to do this.  Just use the --size option to mdadm.

NeilBrown


> 
> If your system is located on the same disks which holds useful data,
> it might be useful to split data into another mountpoint/block device
> and let system skip fs check on startup and produce booted server,
> which is helpful in case of system crash/powerloss and dirty
> fs/breaked raid. RAID assembly problems may be caused by crappy
> controller like lsi 1068e which was hanging the whole system and
> desync data writes on disks on SMART request or completely on it's
> own.
> 
> 
> >
> >
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> 
> 
> 

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