[linux-lvm] Snapshot limit?

[linux-lvm] Snapshot limit?

[Fred van Zwieten]

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Hi,

I would like to know is there is a limit on the amount of snapshots one can
take from a single LV.

I have a single LV with a very low changerate, but I have a retention
requirement of about 150 readonly snapshots for it. Is it is at all
possible, will there be a performance hit?

Fred
**

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Re: [linux-lvm] Snapshot limit?

[Fred van Zwieten]

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O, I forgot: I am using LVM2 on RHEL 6.3. That is LVM2 version 2.02.87.

Met vriendelijke groeten,
*
Fred van Zwieten
*
*Enterprise Open Source Services*
*
Consultant*
*(vrijdags afwezig)*

*VX Company IT Services B.V.*
*T* (035) 539 09 50 mobiel (06) 41 68 28 48
*F* (035) 539 09 08
*E* fvzwieten@vxcompany.com
*I*  www.vxcompany.com



On Mon, Jul 23, 2012 at 10:52 AM, Fred van Zwieten
<fvzwieten@vxcompany.com>wrote:

> Hi,
>
> I would like to know is there is a limit on the amount of snapshots one
> can take from a single LV.
>
> I have a single LV with a very low changerate, but I have a retention
> requirement of about 150 readonly snapshots for it. Is it is at all
> possible, will there be a performance hit?
>
> Fred
> **

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Re: [linux-lvm] Snapshot limit?

[Mike Snitzer]

On Mon, Jul 23 2012 at  5:00am -0400,
Fred van Zwieten <fvzwieten@vxcompany.com> wrote:

> O, I forgot: I am using LVM2 on RHEL 6.3. That is LVM2 version 2.02.87.
> 
> Met vriendelijke groeten,
> *
> Fred van Zwieten
> *
> *Enterprise Open Source Services*
> *
> Consultant*
> *(vrijdags afwezig)*
> 
> *VX Company IT Services B.V.*
> *T* (035) 539 09 50 mobiel (06) 41 68 28 48
> *F* (035) 539 09 08
> *E* fvzwieten@vxcompany.com
> *I*  www.vxcompany.com
> 
> 
> 
> On Mon, Jul 23, 2012 at 10:52 AM, Fred van Zwieten
> <fvzwieten@vxcompany.com>wrote:
> 
> > Hi,
> >
> > I would like to know is there is a limit on the amount of snapshots one
> > can take from a single LV.
> >
> > I have a single LV with a very low changerate, but I have a retention
> > requirement of about 150 readonly snapshots for it. Is it is at all
> > possible, will there be a performance hit?
> >
> > Fred
> > **

You definitely want to make use of the snapshots provided via the new
thinp target (NOTE: thinp is still tech preview in RHEL6.3).

Re: [linux-lvm] Snapshot limit?

[Fred van Zwieten]

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I agree, but that doesn't answer my questions ;-)

Met vriendelijke groeten,
*
Fred van Zwieten
*
*Enterprise Open Source Services*
*
Consultant*
*(vrijdags afwezig)*

*VX Company IT Services B.V.*
*T* (035) 539 09 50 mobiel (06) 41 68 28 48
*F* (035) 539 09 08
*E* fvzwieten@vxcompany.com
*I*  www.vxcompany.com



On Tue, Jul 24, 2012 at 3:15 PM, Mike Snitzer <snitzer@redhat.com> wrote:

> On Mon, Jul 23 2012 at  5:00am -0400,
> Fred van Zwieten <fvzwieten@vxcompany.com> wrote:
>
> > O, I forgot: I am using LVM2 on RHEL 6.3. That is LVM2 version 2.02.87.
> >
> > Met vriendelijke groeten,
> > *
> > Fred van Zwieten
> > *
> > *Enterprise Open Source Services*
> > *
> > Consultant*
> > *(vrijdags afwezig)*
> >
> > *VX Company IT Services B.V.*
> > *T* (035) 539 09 50 mobiel (06) 41 68 28 48
> > *F* (035) 539 09 08
> > *E* fvzwieten@vxcompany.com
> > *I*  www.vxcompany.com
> >
> >
> >
> > On Mon, Jul 23, 2012 at 10:52 AM, Fred van Zwieten
> > <fvzwieten@vxcompany.com>wrote:
> >
> > > Hi,
> > >
> > > I would like to know is there is a limit on the amount of snapshots one
> > > can take from a single LV.
> > >
> > > I have a single LV with a very low changerate, but I have a retention
> > > requirement of about 150 readonly snapshots for it. Is it is at all
> > > possible, will there be a performance hit?
> > >
> > > Fred
> > > **
>
> You definitely want to make use of the snapshots provided via the new
> thinp target (NOTE: thinp is still tech preview in RHEL6.3).
>

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Re: [linux-lvm] Snapshot limit?

[Mike Snitzer]

On Tue, Jul 24 2012 at 10:21am -0400,
Fred van Zwieten <fvzwieten@vxcompany.com> wrote:

> I agree, but that doesn't answer my questions ;-)

please don't top-post.

The old dm-snapshot cannot scale to 150 concurrent read-only
snaps.. sorry.

There would be a 150-way copy out to the 150 different COW areas.  Aka,
the dm-snapshot N-way copy-out penalty

thinp snapshots use a single shared pool for the COW area.