SnapMirror policy clarification

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SnapMirror policy clarification

Ehrenwald, Ian
Hello
I'm trying to understand the differences between the snapshot policies included in cDOT 8.3, namely DPDefault and MirrorAllSnapshots.  The documentation really isn't clear and apparently I can't see it myself.

The behavior I'm seeing with a DP relationship using the DPDefault policy looks like it mirrors all snapshots and the active filesystem, which the MirrorAllSnapshots policy sounds like it should do.  If I delete a snapshot on the source side and do an SM update, the snapshot is gone on the destination side too.

I created a test to try and understand the differences between the policies, but maybe I'm looking at the wrong things because the results of the tests were identical:

- Created testvolA on the source and SM_testvolA on the destination
- Created testvolB on the source and SM_testvolB on the destination
- Created SnapMirror relationship between testvolA and SM_testvolA with a SM policy of MirrorAllSnapshots
- Created SnapMirror relationship between testvolB and SM_testvolB with a SM policy of DPDefault
- Created a snapshot on each source volume
- Initialized SnapMirror relationships
- Examined output of snap list SM_testvol*, identical
- Created another snapshot on each source volume
- Updated SnapMirror relationships
- Examined output of snap list SM_testvol*, identical
- Deleted first snapshot on each source volume
- Updated SnapMirror relationships
- Examined output of snap list SM_testvol*, identical

So, I'm having a difficult time understanding what the point of these policies are.  Can someone enlighten me?


Ian Ehrenwald
Hachette Book Group, Inc.
This may contain confidential material. If you are not an intended recipient, please notify the sender, delete immediately, and understand that no disclosure or reliance on the information herein is permitted. Hachette Book Group may monitor email to and from our network.

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Re: SnapMirror policy clarification

basilberntsen
I've not messed around with these, but they are system created policies. All policies, theoretically even system-created ones, should be able to be seen and compared with snapmirror policy show I think :)

On Fri, Oct 14, 2016 at 10:59 PM, Ehrenwald, Ian <[hidden email]> wrote:
Hello
I'm trying to understand the differences between the snapshot policies included in cDOT 8.3, namely DPDefault and MirrorAllSnapshots.  The documentation really isn't clear and apparently I can't see it myself.

The behavior I'm seeing with a DP relationship using the DPDefault policy looks like it mirrors all snapshots and the active filesystem, which the MirrorAllSnapshots policy sounds like it should do.  If I delete a snapshot on the source side and do an SM update, the snapshot is gone on the destination side too.

I created a test to try and understand the differences between the policies, but maybe I'm looking at the wrong things because the results of the tests were identical:

- Created testvolA on the source and SM_testvolA on the destination
- Created testvolB on the source and SM_testvolB on the destination
- Created SnapMirror relationship between testvolA and SM_testvolA with a SM policy of MirrorAllSnapshots
- Created SnapMirror relationship between testvolB and SM_testvolB with a SM policy of DPDefault
- Created a snapshot on each source volume
- Initialized SnapMirror relationships
- Examined output of snap list SM_testvol*, identical
- Created another snapshot on each source volume
- Updated SnapMirror relationships
- Examined output of snap list SM_testvol*, identical
- Deleted first snapshot on each source volume
- Updated SnapMirror relationships
- Examined output of snap list SM_testvol*, identical

So, I'm having a difficult time understanding what the point of these policies are.  Can someone enlighten me?


Ian Ehrenwald
Hachette Book Group, Inc.
This may contain confidential material. If you are not an intended recipient, please notify the sender, delete immediately, and understand that no disclosure or reliance on the information herein is permitted. Hachette Book Group may monitor email to and from our network.

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http://www.teaparty.net/mailman/listinfo/toasters


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RE: SnapMirror policy clarification

andrei.borzenkov@ts.fujitsu.com
In reply to this post by Ehrenwald, Ian
DPDefault is legacy for traditional (volume based, DP) SnapMirror while MirrorAllSnapshots is for new version-flexible (XDP) SnapMirror. DPDefault works only because traditional DP SnapMirror by definition mirrors full volume with all its content. If you attempt to assign DPDefault to new version-flexible XDP SnapMirror (assuming this is possible, I think it is) it will only mirror AFS, but not other snapshots, because it lacks rule with all_source_snapshots label.

---
With best regards

Andrei Borzenkov
Senior system engineer
FTS WEMEAI RUC RU SC TMS FOS

FUJITSU
Zemlyanoy Val Street, 9, 105 064 Moscow, Russian Federation
Tel.: +7 495 730 62 20 ( reception)
Mob.: +7 916 678 7208
Fax: +7 495 730 62 14
E-mail: [hidden email]
Web: ru.fujitsu.com
Company details: ts.fujitsu.com/imprint
This communication contains information that is confidential, proprietary in nature and/or privileged.  It is for the exclusive use of the intended recipient(s). If you are not the intended recipient(s) or the person responsible for delivering it to the intended recipient(s), please note that any form of dissemination, distribution or copying of this communication is strictly prohibited and may be unlawful. If you have received this communication in error, please immediately notify the sender and delete the original communication. Thank you for your cooperation.
Please be advised that neither Fujitsu, its affiliates, its employees or agents accept liability for any errors, omissions or damages caused by delays of receipt or by any virus infection in this message or its attachments, or which may otherwise arise as a result of this e-mail transmission.


> -----Original Message-----
> From: [hidden email] [mailto:toasters-
> [hidden email]] On Behalf Of Ehrenwald, Ian
> Sent: Saturday, October 15, 2016 5:59 AM
> To: [hidden email]
> Subject: SnapMirror policy clarification
>
> Hello
> I'm trying to understand the differences between the snapshot policies
> included in cDOT 8.3, namely DPDefault and MirrorAllSnapshots.  The
> documentation really isn't clear and apparently I can't see it myself.
>
> The behavior I'm seeing with a DP relationship using the DPDefault
> policy looks like it mirrors all snapshots and the active filesystem,
> which the MirrorAllSnapshots policy sounds like it should do.  If I
> delete a snapshot on the source side and do an SM update, the snapshot
> is gone on the destination side too.
>
> I created a test to try and understand the differences between the
> policies, but maybe I'm looking at the wrong things because the results
> of the tests were identical:
>
> - Created testvolA on the source and SM_testvolA on the destination
> - Created testvolB on the source and SM_testvolB on the destination
> - Created SnapMirror relationship between testvolA and SM_testvolA with
> a SM policy of MirrorAllSnapshots
> - Created SnapMirror relationship between testvolB and SM_testvolB with
> a SM policy of DPDefault
> - Created a snapshot on each source volume
> - Initialized SnapMirror relationships
> - Examined output of snap list SM_testvol*, identical
> - Created another snapshot on each source volume
> - Updated SnapMirror relationships
> - Examined output of snap list SM_testvol*, identical
> - Deleted first snapshot on each source volume
> - Updated SnapMirror relationships
> - Examined output of snap list SM_testvol*, identical
>
> So, I'm having a difficult time understanding what the point of these
> policies are.  Can someone enlighten me?
>
>
> Ian Ehrenwald
> Hachette Book Group, Inc.
> This may contain confidential material. If you are not an intended
> recipient, please notify the sender, delete immediately, and understand
> that no disclosure or reliance on the information herein is permitted.
> Hachette Book Group may monitor email to and from our network.
>
> _______________________________________________
> Toasters mailing list
> [hidden email]
> http://www.teaparty.net/mailman/listinfo/toasters

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Re: SnapMirror policy clarification

Ehrenwald, Ian
Andrei
Thank you for the explanation, that behavior makes sense.  This can be marked as [SOLVED] :)


Ian Ehrenwald
Senior Infrastructure Engineer
Hachette Book Group, Inc.
1.617.263.1948 / [hidden email]

________________________________________
From: [hidden email] <[hidden email]>
Sent: Monday, October 17, 2016 5:53:09 AM
To: Ehrenwald, Ian; [hidden email]
Subject: RE: SnapMirror policy clarification

DPDefault is legacy for traditional (volume based, DP) SnapMirror while MirrorAllSnapshots is for new version-flexible (XDP) SnapMirror. DPDefault works only because traditional DP SnapMirror by definition mirrors full volume with all its content. If you attempt to assign DPDefault to new version-flexible XDP SnapMirror (assuming this is possible, I think it is) it will only mirror AFS, but not other snapshots, because it lacks rule with all_source_snapshots label.

---
With best regards

Andrei Borzenkov
Senior system engineer
FTS WEMEAI RUC RU SC TMS FOS

FUJITSU
Zemlyanoy Val Street, 9, 105 064 Moscow, Russian Federation
Tel.: +7 495 730 62 20 ( reception)
Mob.: +7 916 678 7208
Fax: +7 495 730 62 14
E-mail: [hidden email]
Web: ru.fujitsu.com
Company details: ts.fujitsu.com/imprint
This communication contains information that is confidential, proprietary in nature and/or privileged.  It is for the exclusive use of the intended recipient(s). If you are not the intended recipient(s) or the person responsible for delivering it to the intended recipient(s), please note that any form of dissemination, distribution or copying of this communication is strictly prohibited and may be unlawful. If you have received this communication in error, please immediately notify the sender and delete the original communication. Thank you for your cooperation.
Please be advised that neither Fujitsu, its affiliates, its employees or agents accept liability for any errors, omissions or damages caused by delays of receipt or by any virus infection in this message or its attachments, or which may otherwise arise as a result of this e-mail transmission.


> -----Original Message-----
> From: [hidden email] [mailto:toasters-
> [hidden email]] On Behalf Of Ehrenwald, Ian
> Sent: Saturday, October 15, 2016 5:59 AM
> To: [hidden email]
> Subject: SnapMirror policy clarification
>
> Hello
> I'm trying to understand the differences between the snapshot policies
> included in cDOT 8.3, namely DPDefault and MirrorAllSnapshots.  The
> documentation really isn't clear and apparently I can't see it myself.
>
> The behavior I'm seeing with a DP relationship using the DPDefault
> policy looks like it mirrors all snapshots and the active filesystem,
> which the MirrorAllSnapshots policy sounds like it should do.  If I
> delete a snapshot on the source side and do an SM update, the snapshot
> is gone on the destination side too.
>
> I created a test to try and understand the differences between the
> policies, but maybe I'm looking at the wrong things because the results
> of the tests were identical:
>
> - Created testvolA on the source and SM_testvolA on the destination
> - Created testvolB on the source and SM_testvolB on the destination
> - Created SnapMirror relationship between testvolA and SM_testvolA with
> a SM policy of MirrorAllSnapshots
> - Created SnapMirror relationship between testvolB and SM_testvolB with
> a SM policy of DPDefault
> - Created a snapshot on each source volume
> - Initialized SnapMirror relationships
> - Examined output of snap list SM_testvol*, identical
> - Created another snapshot on each source volume
> - Updated SnapMirror relationships
> - Examined output of snap list SM_testvol*, identical
> - Deleted first snapshot on each source volume
> - Updated SnapMirror relationships
> - Examined output of snap list SM_testvol*, identical
>
> So, I'm having a difficult time understanding what the point of these
> policies are.  Can someone enlighten me?
>
>
> Ian Ehrenwald
> Hachette Book Group, Inc.
> This may contain confidential material. If you are not an intended
> recipient, please notify the sender, delete immediately, and understand
> that no disclosure or reliance on the information herein is permitted.
> Hachette Book Group may monitor email to and from our network.
>
> _______________________________________________
> Toasters mailing list
> [hidden email]
> http://www.teaparty.net/mailman/listinfo/toasters
This may contain confidential material. If you are not an intended recipient, please notify the sender, delete immediately, and understand that no disclosure or reliance on the information herein is permitted. Hachette Book Group may monitor email to and from our network.

_______________________________________________
Toasters mailing list
[hidden email]
http://www.teaparty.net/mailman/listinfo/toasters