How do I gmirror slices?
R. B. Riddick
arne_woerner at yahoo.com
Sat Jan 27 23:09:31 UTC 2007
--- Coen Bröcker <c.brocker at logic-q.nl> wrote:
> Currently ad4 contains 3 partitions:
> ad4s1 swap, / and /var
> ad4s2 /usr
> ad4s3 /home
> I wan't to mirror ad4s1 and ad4s2. I want to stripe ad4s3. Below is my
> current slice setup.
So u have another disk?
Or do u want to mirror ad4s1 to ad4s2? That would be not so wise (performance,
> Offset Size(ST) End Name PType Desc Subtype
> 0 63 62 - 12 unused 0
> 63 12578832 12578894 ad4s1 8 freebsd 165
> 12578895 147814065 160392959 ad4s2 8 freebsd 165
> 160392960 425706435 586099394 ad4s3 8 freebsd 165
> 586099395 15309 586114703 - 12 unused 0
> Before I continue setting up the mirror I want to make sure I've setup my
> slices correctly.
> Reading the gmirror man page it states that the gmirror utility uses on-disk
> metadata (stored in the provider's last sector) to store all needed
> Since I'm no expert in understanding disk structures I'm not sure what the
> above means.
gmirror/gstripe use the last sector of its consumers for meta data, and provide
a device that is one sector shorter than the smalles consumer.
gmirror(name=X, consumers=(ad99s1(size=1GB), ad77(size=2GB)), size=1GB-512B)
> In my case I think I should create the folowing slice setup:
> my last partition on ad4s1 must end at 12578893 instead of 12578894. The
> next partition should begin at 12578895 and end at 160392958 creating the
> space to store metadata.
The problem with an existing installation is, that it is possible that the last
sector of ad4s1 and ad4s2 and ad4s3 is used by a file system. So we need to
know the bsdlabel of ad4s1 and ad4s2 and ad4s3 in order to give useful advice.
I just wonder why u want to stripe (without any safety) the home fs, which
contains most likely quite important and difficult to restore data, while u
want to mirror (with disk failure protection) the root-fs (/), although u can
just put a CD into ur box and restore it... R u sure, that u dont want to
mirror ur home fs, too (or graid3 (e. g. 2disks (data) +1disk (parity)) or so)?
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