[lug] re-partition the primary master

[D. Stimits]

John Karns wrote:
> 
> On Fri, 28 Jun 2002, Paul Bille said:
> 
> > It's a dual boot system with LINUX and Windows installed on the master
> > 10gb drive partitioned as follows: Primary Master 10GB
> >       hda1    2048mb          /dos
> >       hda2     104mb          /
> >       hda3     104mb          LINUX swap
> >       hda5    1542mb          /usr
> >       hda7      54mb          /var
> >       hda8    6063mb          /home
> >
> > There is a 1.6GB slave with Windows data and an unused Win operating
> > system: Secondary Slave 1.6GB
> >       hdb1    1584mb          Win FAT32
> >
> > I have a /usr partition with 1.5GB that is only %72 utilized with RH 7.0
> > but apparently RH 7.3 needs > 2GB.  I wonder if I'll be able to
> > re-partition to take some of the space from /home and use it for /usr
> > without loosing all the data in /usr.
> 
> Then using the Multiple devices driver support capability of the kernel,
> why can't you break up the /home partition into two smaller pieces, and
> "append" one of them to /usr?  I haven't done it myself, but the
> description seems to fit the situation:

Part of the original question was how to do it without destroying the
data. When creating an MD device, it is 100% destructive. But it would
be possible to combine multiple unrelated partitions into one larger
virtual partition, which in turn can become /home. I would not recommend
the complications of MD unless there is a big reason for it. Append mode
is not RAID, and does not benefit performance, but would allow appending
odd partitions together. If the partitions can be of approximately the
same size, then RAID 0 striping would be a bonus in performance, but any
one partition dying would take the whole set of combined partitions
down, so that is the tradeoff.

NOTE: Even a small difference in partition characteristics among the
multiple partitions that make up a RAID 0 (and some other modes) MD has
a dramatic impact on performance.

D. Stimits, stimits at idcomm.com

> 
> Multiple devices driver support
> CONFIG_BLK_DEV_MD
> 
>   This driver lets you combine several hard disk partitions into one
>   logical block device. This can be used to simply append one
>   partition to another one or to combine several redundant hard disks
>   into a RAID1/4/5 device so as to provide protection against hard
>   disk failures. This is called "Software RAID" since the combining of
>   the partitions is done by the kernel. "Hardware RAID" means that the
>   combining is done by a dedicated controller; if you have such a
>   controller, you do not need to say Y here.
> 
> ----------------------------------------------------------------
> John Karns                                        jkarns at csd.net
> 
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