lkml.org 
[lkml]   [1998]   [Nov]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: New Solaris 7 features

    On Tue, 10 Nov 1998, Malcolm Beattie wrote:

    > While I'm here: an idea for providing a snapshot capability to any
    > block device (allowing you to snapshot then backup any fs you like).

    this is a planned feature of the MD based LVM personality i'm working on.
    The prototype of the LVM is already in the latest MD patch
    (http://www.kernel.org/pub/linux/daemons/raid/alpha/), the snapshot
    feature will probably show up in the next release. (in a few days)

    > A fake block device /dev/snap which you connect to the
    > device-to-be-snapshotted on one side and to a spare block device on
    > the other side (either a spare partition or a /dev/loop on a file).

    the snapshotted device does a 'copy-out' to a 'store old contents' device
    for every (block) write after the snapshot time. The 'old contents' device
    is some scratch partition or an on-demand-storage LVM device. (ie. if the
    device runs out of space, it will not fail, it can self-extend itself)

    > snap keeps a dirty bitmap and a sparse block structure on the spare
    > block device. Writes to snap mark the block in the dirty bitmap and
    > store the original block in the sparse structure. Reads from snap
    > check the dirty bitmap and read from the original or the sparse block
    > map.

    we do not want to write to the 'snap'. We want to use the 'snapshot
    device' to carry a snapshot for some limited (or unlimited) time, eg. for
    backup purposes. This thing is completely transparent to the 'normal'
    device.

    -- mingo



    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.rutgers.edu
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 13:45    [W:6.950 / U:0.016 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site