Date: Sun, 17 Jan 2010 21:42:49 +0000 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: Mike Clarke <jmc-freebsd2@milibyte.co.uk> Cc: Pieter de Goeje <pieter@degoeje.nl>, freebsd-questions@freebsd.org Subject: Re: Newbie gmirror questions Message-ID: <4B538459.7090601@infracaninophile.co.uk> In-Reply-To: <201001172122.15128.jmc-freebsd2@milibyte.co.uk> References: <201001152334.52978.jmc-freebsd2@milibyte.co.uk> <201001171639.41777.jmc-freebsd2@milibyte.co.uk> <4B534661.7030905@infracaninophile.co.uk> <201001172122.15128.jmc-freebsd2@milibyte.co.uk>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigDC673569D521166F44C4F3D6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Mike Clarke wrote: > On Sunday 17 January 2010, Matthew Seaman wrote: >=20 >> Mike Clarke wrote: >>> Actually I was more concerned about what happens when I boot into >>> another OS like Windows or Linux on one of the spare slices - I'm >>> assuming that I have to apply gmirror to the whole disk rather than >>> just selected slices? >> You can't do this. gmirror is FreeBSD specific, and other OSes can't >> deal with it. You can take your two drives, partition them (fdisk) >> and then create a gmirror across the slices you assign to FreeBSD. >=20 > This will make things a lot easier for me. I think all the examples of = > gmirror I've seen used things like /dev/da0 as the provider in label=20 > commands so I assumed that I had to use the whole physical disk but if = > I can mirror individual slices then I have much more flexibility. >=20 > My motherboard has a UDMA133 controller for ata0 & ata1 (which I don't = > use) and 2 SATA controllers for ata2 to ata5 so with my 2 SATA drives=20 > spread between the controllers on channels 2 & 4 I could have something= =20 > like /dev/mirror/gm1 provided by /dev/ad2s1 & /dev/ad4s1=20 > and /dev/mirror/gm2 provided by /dev/ad2s2 & /dev/ad4s2 for a couple of= =20 > FreeBSD systems. That will leave me with 2 spare slices on each drive=20 > for other purposes. Any Windows or Linux stuff I put on tends to be=20 > mainly experimental and less long term than my FreeBSD system so don't = > really need the resilience of being mirrored. >=20 Yes -- there's an On-Lamp article by Dru Lavigne that has been particular= ly influential, and gmirror'ing whole disks is the best way forwards for the= vast majority of cases where you've a server dedicated to one OS. However, one of the really amazingly brilliant things about geom is that just about any disk / storage related thing can be a geom provider, and=20 geom constructs will nest very happily. Here's a howto for setting up gmirror across a pair of slices: http://people.freebsd.org/~rse/mirror/ It's fairly old now, but the essentials are still correct. The one thing= that has changed in the intervening time is what is the best algorithm to use for the gmirror. Up until the release of 8.0, 'round-robin' was=20 virtually always the right choice, but nowadays 'load' is preferred. All that means, is change the following line in rse's article from: gmirror label -v -n -b round-robin ${gm} /dev/${d2}s1 to gmirror label -v -n -b load ${gm} /dev/${d2}s1 Cheers, Matthew --=20 Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW --------------enigDC673569D521166F44C4F3D6 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEAREIAAYFAktThF4ACgkQ8Mjk52CukIwwfACeOmZuTNFrWqyYKSD7f2r5xKZ6 j6IAoITJjkmu5GxJoL9xBL/ZmQ7T149H =VqSw -----END PGP SIGNATURE----- --------------enigDC673569D521166F44C4F3D6--
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