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Date:      Sun, 9 Jul 2006 17:57:59 +0200
From:      Paul Schenkeveld <fb-geom@psconsult.nl>
To:        freebsd-geom@freebsd.org
Subject:   Which geom to use?
Message-ID:  <20060709155759.GA67709@psconsult.nl>

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Hi,

Some installations just need a lot of filesystems (e.g. systems with
many jails) making geom_bsd a bad choice because it only supports
7 partitions.  So far I've been using vinum and gvinum for the task
of dividing my disk which is also quite convinient for adding new
partitions in so far unallocated space later on.

On systems with mirrored disks (or RAID5) this works fine but on
systems with a single disk this approach has a very bad consequence:
when a disk error occurs anywhere on the disk, all subdisk and thus
all volumes on this drive object become invalid and the system crashes.

Another approach is to slice up the disk in MBR and divide each slice
in 7 patitions with bsdlabel giving you 28 partitions to use and less
freedom to re-allocate later on because it's a very hard job to change
the MBR slices without doing a complete re-partitioning.

I've heard of people putting filesystems in files using md(4) but I
fear the performance penalty of going through a filesystem layer twice.

So what would you guys recommend in this case, gpt(4)?  Or is there some
kind of geom that does just the volume management of gvinum without
marking all volumes down at the first media error?

Regards,

Paul Schenkeveld



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