All of lore.kernel.org
 help / color / mirror / Atom feed
From: Tomasz Chmielewski <mangoo@wpkg.org>
To: linux-lvm@redhat.com, mvijai@novell.com, dm-devel@redhat.com
Subject: Re: [RFC] Multiple Snapshots - Manageability problem
Date: Wed, 23 Jan 2008 17:16:42 +0100	[thread overview]
Message-ID: <4797686A.4000306@wpkg.org> (raw)

Vijai Babu Madhavan, Thu, 11 Jan 2007 11:18:13 -0700, wrote:

> The problem of DM snapshots with multiple snapshots have been discussed 
> in the lists quiet a bit (Most recently @ 
> https://www.redhat.com/archives/dm-devel/2006-October/msg00034.html).
> 
> We are currently in the process of building a DM snapshot target that scales 
> well with many snapshots (so that the changed blocks don't get copied to each 
> snapshot). In this process, I would also like to validate an assumption.
> 
> Today, when a single snapshot gets created, a new cow device of a given size 
> is also created. IMO, there are two problems with this approach:
> 
> a) It is difficult to predict the size of the cow device, which requires a prediction 
> of the number of writes would go into the origin volume during the snapshot 
> life cycle. It is difficult to get this prediction right, as very high value reduces 
> utilization and low value increases the chances of snapshot becoming full.
> 
> b) A new cow device needs to be created every time.

Hi,

Any news on that?

Still, with multiple snapshots write performance degrades linearly - is 
any work done to change that anytime soon?



-- 
Tomasz Chmielewski
http://wpkg.org

_______________________________________________
linux-lvm mailing list
linux-lvm@redhat.com
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

WARNING: multiple messages have this Message-ID (diff)
From: Tomasz Chmielewski <mangoo@wpkg.org>
To: linux-lvm@redhat.com, mvijai@novell.com, dm-devel@redhat.com
Subject: [linux-lvm] Re: [RFC] Multiple Snapshots - Manageability problem
Date: Wed, 23 Jan 2008 17:16:42 +0100	[thread overview]
Message-ID: <4797686A.4000306@wpkg.org> (raw)

Vijai Babu Madhavan, Thu, 11 Jan 2007 11:18:13 -0700, wrote:

> The problem of DM snapshots with multiple snapshots have been discussed 
> in the lists quiet a bit (Most recently @ 
> https://www.redhat.com/archives/dm-devel/2006-October/msg00034.html).
> 
> We are currently in the process of building a DM snapshot target that scales 
> well with many snapshots (so that the changed blocks don't get copied to each 
> snapshot). In this process, I would also like to validate an assumption.
> 
> Today, when a single snapshot gets created, a new cow device of a given size 
> is also created. IMO, there are two problems with this approach:
> 
> a) It is difficult to predict the size of the cow device, which requires a prediction 
> of the number of writes would go into the origin volume during the snapshot 
> life cycle. It is difficult to get this prediction right, as very high value reduces 
> utilization and low value increases the chances of snapshot becoming full.
> 
> b) A new cow device needs to be created every time.

Hi,

Any news on that?

Still, with multiple snapshots write performance degrades linearly - is 
any work done to change that anytime soon?



-- 
Tomasz Chmielewski
http://wpkg.org

             reply	other threads:[~2008-01-23 16:16 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-23 16:16 Tomasz Chmielewski [this message]
2008-01-23 16:16 ` [linux-lvm] Re: [RFC] Multiple Snapshots - Manageability problem Tomasz Chmielewski
2008-01-23 22:36 ` Dan Kegel
2008-01-23 22:36   ` [linux-lvm] " Dan Kegel
2008-01-24 11:02   ` Tomasz Chmielewski
2008-01-24 11:02     ` [linux-lvm] " Tomasz Chmielewski
2008-01-24 13:18     ` Dan Kegel
  -- strict thread matches above, loose matches on Subject: below --
2007-01-11 18:18 Vijai Babu Madhavan
2007-01-11 21:34 ` Wilson, Christopher J
2007-01-12  4:46   ` Vijai Babu Madhavan
2007-01-12 21:59 ` Benjamin Marzinski
2007-01-30  4:39   ` Mike Snitzer
2007-03-04 15:55     ` Dan Kegel

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=4797686A.4000306@wpkg.org \
    --to=mangoo@wpkg.org \
    --cc=dm-devel@redhat.com \
    --cc=linux-lvm@redhat.com \
    --cc=mvijai@novell.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.