From mboxrd@z Thu Jan 1 00:00:00 1970 From: haad Subject: Re: LVM Snapshot Feature Date: Wed, 6 Aug 2008 09:08:16 +0300 Message-ID: <70f06bad0808052308p6fc03511web87ab414e650c81@mail.gmail.com> References: <4DE0C34D8B0DA64C9585DC45C36EA03BAB0788@dewdfe1g.wdf.sap.corp> <1746B17C-CC23-40D7-A993-FC32CAA5BF24@gmail.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development List-Id: dm-devel.ids On Mon, Aug 4, 2008 at 4:15 PM, Mikulas Patocka wrote: > On Fri, 1 Aug 2008, Adam Hamsik wrote: > >> On Aug,Friday 1 2008, at 9:35 AM, Bombardier, Pascal wrote: >> >> > Hi, >> > >> > In your opinion, does it make sense to be able to create non-persistent >> > snapshots ? >> > In the case of a filesystem backup, a non-persistent snapshot would be a >> > snapshot that we agree to lose in case of failure or reboot. If anything >> > happens, a server administrator would have to recreate a new snapshot >> > and then restart the backup. >> > In this case, I think metadata could be stored in memory instead of on >> > disk, which should improve LVM snapshot performance. >> > >> > Is this theory wrong, and is this something which can be implemented >> > easily in the current LVM code ? >> > >> >> AFAIK non-persistent snapshots are already implemented see >> DM_PERSISTENT_DEV_FLAG ? I haven't look at linux kernel code how is >> it done but when I solve my lvcreate -s bug on NetBSD non-persistent >> snapshots are next :). >> >> Regards >> >> Adam. > > Yes. They are implemented in device mapper in kernel --- but no userspace > lvm tool can use them. You can only create them using dmsetup. > > Mikulas Do you have list of commands which I have to run to create persistent dm snapshot with dmsetup ? It would be handy to test my driver with dmsetup first and only after that use lvm2tools to create persistent/non-persistent snapshots. Regards Adam.