Legacy HDS Forums

HUR + CCI + HRpM - Definitions & Design Clarifications Required

Discussion created by Legacy HDS Forums on Jan 19, 2012
Latest reply on Oct 27, 2014 by Michael Ratner

Originally posted by: arappoport

 

Hi there,

 

I am trying to untangle the different objects involved in HUR (Hitachi Universal Replicator asynchronous remote replication) for Open Systems, HRpM (Replication Manager) and CCI (Command Control Interface).

 

## Let's start with some HUR Architecture basics:
In order to replicate asynchronously data volumes from array to array, HUR leverages the following elements to ensure data and write order consistency:

 

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[*]Data Volumes

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Data Volumes are the primary (source) and secondary (target) LDEVs containing your business data. P-Vols and S-Vols.

 

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[*]Journal Volumes (JNL Vols)
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JNL Vols are reserved LDEVs storing differential data (update data) and metadata. For each array, they are linked to data volumes. For P-Vols, they are called Master or Primary JNL Vols. For S-Vols, they are called Restore or Secondary JNL Vols.

 

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[*]Journal Group or Journal (JNLG or JNL)
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Journal Group is a logical group made of the data volumes and related JNL volumes. You can have up to 256 JNL Groups per array (16 recommended), up to 64 JNL Vols per JNL Group, and over 8000 data volumes per JNL Group.

 

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[*]Mirror (MU#)
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Mirror is the established relationship between primary and secondary JNL Groups. JNL Groups in a mirror relationship do not have to have the same id. You can have up to 4 mirrors. Used for cascaded or MxN setups. HUR Mirrors are identified with a "h" in front of the MU#.

 

## Now let's add and mix some CCI Architecture basics:

 

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[*]CCI Device Group (dev_group) or Copy Group
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Group of replication pairs. It allows you to group pairs across multiple arrays (MxN), so it's a nice feature.
It creates the idea of consistency across all pairs under the same dev_group, but it can be composed (in MxN) of multiple JNLGs.

 

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[*]Consistency Group (CCI CTG)
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CCI guarantees consistency for replication pairs assigned to the same CTGID. A CCI CTG is not a CCI copy group or HORCM dev group (watch out HDS swapped definitions for the VSP with HORCM_LDEVG). By default, a pair must be created within a copy group with a CTGID, and CCI allocates the same CTGID for pairs under the same copy group, so that's why it goes unnoticed.
For HUR, best practice is to match the CTGID with the JNLG ID, for obvious reasons.

 

## and finally let's add some HRpM Architecture basics:

 

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[*]Pair Group

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HRpM separates replication or copy types as Pair Groups, your pick from HUR, TCS, TCA, SI, CoW.

 

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[*]Copy Group

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HRpM Copy Group is simply your CCI Device Group.

So I hope I documented this ensemble correctly.

 

kind regards,
Alex Rappoport

 

Message was edited by: Michael Ratner

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