How to create a SymClone image of a SRDF (R2) diskgroup image when using Veritas Volume Manager and DMP
Article ID: 100037840
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Description
Description
This document attempts to explain the steps required to create an EMC SymClone image of an EMC SRDF (R2) VxVM (Veritas Volume Manager) controlled diskgroup using Veritas DMP as the multipathing driver.
In this instance, the following configuration consists of "4" EMC SRDF "R1" devices presented to production server "Dopey" from EMC Symmetrix id (SID) "822".
An additional "4" EMC SRDF "R2" devices have been presented to DR server "Bashful" from EMC Symmetrix ID (SID) "414".
Note: As of 5.0 MP3 onwards, the VxVM CLI command "vxdisk -e list" is capable of reporting the extended attribute based content for EMC BCV, BCV-NR, MIRROR, SRDF-R1, SRDF-R2, TDEV device states and EMC lun types.
Figure 1.0
BCV vs SymClone
EMC provides the ability to create cloned copies of data simultaneously on multiple target devices from a single source device. The data is available to the same (local) or target host instantly.
Note: You can copy data from a single source device to as many as sixteen target devices.
A source device can be either a Symmetrix standard (std) device or a BCV device. The target device is a Symmetrix clone that contains an exact copy of the source device.
The BCV lun is an EMC Symmetrix device with special attributes created when the Symmetrix is configured. It can function either as an additional mirror to an existing Symmetrix device or as an independent device.
Establishing BCV devices as mirror images of active production data, allows multiple simultaneous business continuance tasks to be performed in parallel. The principal (source) device, known as the standard (std) device, remains online for regular Symmetrix operations on the original production server.
Each BCV is unique, making it accessible to the production server, or a separate backup/disaster recovery (DR) server.
The EMC symmir command forms an relationship between the std and BCV device when placed in an "established" state.
As a mirror of a standard device, the relationship is known as a BCV pair. The BCV device is temporarily inaccessible to its host until the BCV pair is "split".
A SymClone (clone) can be either an EMC Symmetrix standard (std) device, or an EMC BCV device, that is to be the clone copy (target device) of another EMC Symmetrix device. Unlike a BCV mirror copy, which must be completely synchronized with its source, and then split to access the data, the clone copy activation functionality makes the cloned disk image (data) immediately accessible to its host, even whilst copying is occurring in the background. The EMC symclone commands are used to create and activate a source/target clone pair.
Steps:
In this instance, an EMC SymClone image will be taken of the EMC SRDF lun "emc1_0072" to SymClone(clone) lun "emc1_00dd".
1.] VxVM disk listing:
Bashful # vxdisk -eo alldgs list
DEVICE TYPE DISK GROUP STATUS OS_NATIVE_NAME ATTR
emc1_00dc auto:cdsdisk - - online c1t5006048C536979A0d80s2 bcv
emc1_00dd auto:cdsdisk - - online c1t5006048C536979A0d81s2 bcv <<<< EMC Symclone of EMC SRDF (R2) lun "emc0_0072"
emc1_0072 auto:cdsdisk - (DopeyDg) online c1t5006048C536979A0d65s2 srdf-r2 <<<< Source EMC SRDF (R2) lun
emc1_0073 auto:cdsdisk - (DopeyDg) online c1t5006048C536979A0d66s2 srdf-r2
emc1_0074 auto:cdsdisk - (DopeyDg) online c1t5006048C536979A0d67s2 srdf-r2
emc1_0075 auto:cdsdisk - (DopeyDg) online c1t5006048C536979A0d68s2 srdf-r2
2.] As the EMC SRDF lun is already part of an existing EMC "DeviceGroup", a mapping file can be created and parsed by the EMC "symmir" command.
Bashful # cat /symclone_mappings.txt
0072 00DD
The EMC SYMDEV reference in the first column is the source lun "0072", which relates to Veritas disk access (da) name "emc1_0072".
The EMC SYMDEV reference in the second column is the target lun "00DD" for the EMC SymClone device, which relates to Veritas disk access (da) name "emc0_00dd".
3.] Using the above "mapping" file, the source to target device mappings will be formed.
The EMC Symmetrix ID (SID) can be obtained from the Veritas DMP CLI command "vxdmpadm listenclosure all".
In this instance, the SID is " 000290301 414 ", for which can be shortened to just three characters in length "414".
Bashful # vxdmpadm listenclosure all
ENCLR_NAME ENCLR_TYPE ENCLR_SNO STATUS ARRAY_TYPE LUN_COUNT
===================================================================================
emc1 EMC 000290301414 CONNECTED A/A 6
4.] UDID content.
The UDID (Unique Disk Identifier) is composed of the VID (Vendor ID), PID (Product ID), CAB_SERIAL_NO (Enclosure Serial Number) and LUN_SERIAL_NO (LUN serial number).
Note: The "udid" value represents the UDID from the DDL (Device Discovery Layer). The second "udid_asl" value represents the UDID that is held on disk.
Prior to the target (SymClone) lun being overwritten with the contents of the source lun , the UDID values for the target lun are aligned.
Device: emc1_00dd
udid: EMC%5FSYMMETRIX%5F000290301414%5F60060480000290301414533030304444
tag udid_asl=EMC%5FSYMMETRIX%5F000290301414%5F60060480000290301414533030304444
Device: emc1_0072
udid: EMC%5FSYMMETRIX%5F000290301414%5F60060480000290301414533030303732 <<<
tag udid_asl=EMC%5FSYMMETRIX%5F000290300822% 5F60060480000290300822533030303843
Note: The UDID values of the source lun (SRDF R2) are not in sync, as the on-disk UDID value for the source lun contains the UDID from the SRDF "R1" lun.
The server "Dopey" contains the SRDF "R1" luns.
Note: Veritas disk access (da) name "emc0_008c" from the server "Dopey", is replicated to server "Bashful" with a Veritas disk access name of "emc1_0072".
Dopey # vxdisk -v list emc0_008c | egrep '(Device|udid)'
Device: emc0_008c
udid: EMC%5FSYMMETRIX%5F000290300822% 5F60060480000290300822533030303843
tag udid_asl=EMC%5FSYMMETRIX%5F000290300822% 5F60060480000290300822533030303843
5.] SymClone functionality.
The SymClone operation enables the user to copy data from a single source device to as many as sixteen target devices, with automatic background copying of up to four target devices simultaneously.
The target of a copy operation is referred to as an EMC Symmetrix clone.
Copying to a clone device can be either immediate or deferred:
• A deferred copy. Those tracks on a device that contain the data of most interest. Copying occurs when there are writes to the source device or reads/writes to the target device. The clone pair state remains CopyOnAccess until the copy session is terminated or all tracks have been accessed.
-copy Causes the device copy to take place in the background.
Normally, the copying of tracks is not completed unless the source device is written to, or the target device is read or written to.
When the create -copy operation executes, the state of the device pair is CopyInProgress.
If and when all the tracks are eventually moved to the target device, the state changes to Copied.
• An immediate copy of the full source device to the target device requires the –precopy option.
-precopy Causes the device copy to take place in the background before the activate starts.
Normally, the copying of tracks is not started until the activate occurs.
The precopy process continuously runs in the background until the activate is called.
The clone pair state is CopyInProgress until the clone pair reaches the Copied state.
Additional options such as "–differential" are available with later releases of the EMC Solutions Enabler software and array firmware, which means that any subsequent clone operation will copy only the changed data.
When creating EMC SymClones, the source or the target device can be either a standard (std) device or BCV device, however, they must be of the same emulation type. The target device must also be the same size as the source device. The cloning process of a source device to a target device is performed within the same EMC Symmetrix array.
6.] Start the SymClone copy using "-precopy" option.
Note: When the SymClone "create" command is issued, the target device is placed in a Not-Ready (NR) state.
This operation then configures the "track protection bitmap" to provide user access to the cloned data, as soon as the clone pair is activated.
The target device is made "ready" again when the SymClone "activate" command operation has completed. Upon completion, the user on the target's host can then access the data on the target device immediately:
Bashful # symclone -sid 414 -v -f /symclone_mappings.txt create -precopy
Execute 'Create' operation for the 1 specified device(s)
in device file '/symclone_mappings.txt' (y/[n]) ? y
'Create' operation execution is in progress for the device list in
device file '/symclone_mappings.txt'. Please wait...
SELECTING the list of Source devices in the group:
Device: 0072 [SELECTED]
SELECTING Target devices in the group:
Device: 00DD [SELECTED]
PAIRING of Source and Target devices:
Devices: 0072(S) - 00DD(T) [PAIRED]
STARTING a Clone 'CREATE' operation.
The Clone 'CREATE' operation SUCCEEDED.
'Create' operation successfully executed for the device list
in device file '/symclone_mappings.txt'.
7.] Query SymClone copy state
Bashful # symclone -sid 414 -v -f /symclone_mappings.txt query
SELECTING the list of Source devices in the group:
Device: 0072 [SELECTED]
SELECTING Target devices in the group:
Device: 00DD [SELECTED]
PAIRING of Source and Target devices:
Devices: 0072(S) - 00DD(T) [PAIRED]
Device File Name : /symclone_mappings.txt
Device's Symmetrix ID : 000290301414
Source Device Target Device State Copy
--------------------------------- ---------------------------- ------------ ----
Protected Modified Modified
Logical Sym Tracks Tracks Logical Sym Tracks CGDP SRC <=> TGT (%)
--------------------------------- ---------------------------- ------------ ----
N/A 0072 16128 0 N/A 00DD 0 X... PreCopy 49
Total -------- -------- --------
Track(s) 16128 0 0
MB(s) 1008.0 0.0 0.0
Legend:
(C): X = The background copy setting is active for this pair.
. = The background copy setting is not active for this pair.
(G): X = The Target device is associated with this group.
. = The Target device is not associated with this group.
(D): X = The Clone session is a differential copy session.
. = The Clone session is not a differential copy session.
(P): X = The pre-copy operation has completed one cycle
. = The pre-copy operation has not completed one cycle
8.] Example of SymClone "-copy" operation
For illustration purposes only:
Bashful # symclone -sid 414 -v -f /symclone_mappings.txt create -copy
Execute 'Create' operation for the 1 specified device(s)
in device file '/symclone_mappings.txt' (y/[n]) ? y
'Create' operation execution is in progress for the device list in
device file '/symclone_mappings.txt'. Please wait...
SELECTING the list of Source devices in the group:
Device: 0072 [SELECTED]
SELECTING Target devices in the group:
Device: 00DD [SELECTED]
PAIRING of Source and Target devices:
Devices: 0072(S) - 00DD(T) [PAIRED]
STARTING a Clone 'CREATE' operation.
The Clone 'CREATE' operation SUCCEEDED.
'Create' operation successfully executed for the device list
in device file '/symclone_mappings.txt'.
Bashful # symclone -sid 414 -v -f /symclone_mappings.txt query
SELECTING the list of Source devices in the group:
Device: 0072 [SELECTED]
SELECTING Target devices in the group:
Device: 00DD [SELECTED]
PAIRING of Source and Target devices:
Devices: 0072(S) - 00DD(T) [PAIRED]
Device File Name : /symclone_mappings.txt
Device's Symmetrix ID : 000290301414
Source Device Target Device State Copy
--------------------------------- ---------------------------- ------------ ----
Protected Modified Modified
Logical Sym Tracks Tracks Logical Sym Tracks CGDP SRC <=> TGT (%)
--------------------------------- ---------------------------- ------------ ----
N/A 0072 32250 0 N/A 00DD 0 X... Created 0
Total -------- -------- --------
Track(s) 32250 0 0
MB(s) 2015.6 0.0 0.0
Legend:
(C): X = The background copy setting is active for this pair.
. = The background copy setting is not active for this pair.
(G): X = The Target device is associated with this group.
. = The Target device is not associated with this group.
(D): X = The Clone session is a differential copy session.
. = The Clone session is not a differential copy session.
(P): X = The pre-copy operation has completed one cycle
. = The pre-copy operation has not completed one cycle
9.] After some time, the SymClone state will be reported with a "100%" PreCopy state.
Issue/Introduction
