Re: [linux-lvm] Newbie to snapshot

["Heinz J . Mauelshagen" <mauelshagen@sistina.com>]

On Sun, May 18, 2003 at 10:58:23PM +0800, armani wrote:
> Thanks for toby's explainations!
> ==
> Eventually I create a new snapshot of my LV partition.
> But I have another problem with the snapshot of LV.
> That is how much snapshot I could create for my LV partition ?
> As I know some commercial software could create 254 snapshots for one LV
> such as IBM.
> 
> So I try to create another snapshot for LV by issuing the following command:
> 
> This is my first snapshot for /dev/Vol1/LV1
> 
> [root@met root]# lvcreate --size 100M -s -nsnapshot /dev/Vol1/LV1
> lvcreate -- WARNING: the snapshot will be automatically disabled once it
> gets full
> lvcreate -- INFO: using default snapshot chunk size of 64 KB for
> "/dev/Vol1/snapshot"
> lvcreate -- doing automatic backup of "Vol1"
> lvcreate -- logical volume "/dev/Vol1/snapshot" successfully created
> 
> I tried to create another snapshot for /dev/Vol1/LV1
> 
> [root@met root]# lvcreate --size 100M -s -nsnapshot1 /dev/Vol1/LV1
> lvcreate -- WARNING: the snapshot will be automatically disabled once it
> gets full
> lvcreate -- INFO: using default snapshot chunk size of 64 KB for
> "/dev/Vol1/snapshot1"
> lvcreate -- doing automatic backup of "Vol1"
> lvcreate -- logical volume "/dev/Vol1/snapshot1" successfully created
> 
> And how can I estimate the sizes and counts for them ?

lvdisplay /dev/Vol1/snapsh*

> Is there any rules or principles to formalize the procedures ?

There's no tool in the LVM distro for that so far.
You can write a script (Shell, Perl, ...) around lvdisplay to
create alerts when a snapshot runs out of space or extend it automatically.

> 
> 
> > A snapshot will only capture what you have in the fs at the moment you
> -- snip --
> > -toby
> 
> -- Armani Liao
> 
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@Sistina.com                           +49 2626 141200
                                                       FAX 924446
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