From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 29 Aug 2001 17:31:24 -0500 From: AJ Lewis Subject: Re: [linux-lvm] Snapshot sizes Message-ID: <20010829173123.A10331@sistina.com> References: Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-md5; protocol="application/pgp-signature"; boundary="mP3DRpeJDSE+ciuQ" Content-Disposition: inline In-Reply-To: ; from gasht@neopets.com on Wed, Aug 29, 2001 at 03:05:30PM -0700 Sender: linux-lvm-admin@sistina.com Errors-To: linux-lvm-admin@sistina.com Reply-To: linux-lvm@sistina.com List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: List-Id: To: linux-lvm@sistina.com --mP3DRpeJDSE+ciuQ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Aug 29, 2001 at 03:05:30PM -0700, Gashaw Teshome wrote: > I would like to use snapshotting to backup an LVM-based machine. The fil= es=20 > that I want to backup total about 20G, while LV is about 100G. What size= do=20 > I need to make the snapshot volume to allow for this much data? >=20 > Please let me know if I need to add any more information to make myself= =20 > clearer. You need enough room in the snapshot to store all the changes written to the disk from the time you take the snapshot to the time you finish backing it up. What happens is that when there is a write pending to the original LV, we first copy the original data to the snapshot LV, then write the new data to the original LV. The snapshot only stores the changed data. It redirects any queries of data that hasn't changed back to the data stored on the original LV. Make sense? There is more detailed information at: http://tech.sistina.com/lvm/doc/lvm_howto/Taking_a_backup_using_sna.html#se= c:Snapshots_Backup Regards, --=20 AJ Lewis Sistina Software Inc. Voice: 612-638-0500 1313 5th St SE, Suite 111 Fax: 612-638-0500 Minneapolis, MN 55414 E-Mail: lewis@sistina.com http://www.sistina.com Current GPG fingerprint =3D 3B5F 6011 5216 76A5 2F6B 52A0 941E 1261 0029 2= 648 Get my key at: http://people.sistina.com/~lewis/gpgkey (Unfortunately, the PKS-type keyservers do not work with multiple sub-keys) -----Begin Obligatory Humorous Quote---------------------------------------- A computer without a Microsoft operating system is like a dog without bricks tied to its head. -----End Obligatory Humorous Quote------------------------------------------ --mP3DRpeJDSE+ciuQ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE7jW07pE6/iGtdjLERAhslAJ9AolRALHN+mWB6imZQsieMDj4yzwCfe+Yh U8itCv7bY0EpEgffCrzc4EI= =5VBg -----END PGP SIGNATURE----- --mP3DRpeJDSE+ciuQ--