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Description
This document attempts to explain the steps required to split the EMC SRDF relationship when using Veritas Volume Manager (VxVM) and DMP.
EMC SRDF logically pairs a device or a group of devices from each array and replicates data from one to the other synchronously or asynchronously. An established pair of devices can be split, so that separate hosts can access the same data independently (maybe for backup), and then resynchronized.
In this instance, the 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".
In synchronous mode (SRDF/S), the primary array waits until the secondary array has acknowledged each write before the next write is accepted, ensuring that the replicated copy of the data is always as current as the primary. However, the latency due to propagation increases significantly with distance.
In asynchronous mode (SRDF/A) transfers the changes to the secondary array in units called delta sets, which are transferred at defined intervals. Although the remote copy of the data will never be as current as the primary copy, this method can replicate data over considerable distances and with reduced bandwidth requirements and mimimal impact on host performance.
Figure 1.0
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.
Example
In this instance, the local EMC SYMDEVs are 008C, 008D, 008E and 008F. The remote EMC SYMDEVs are 0072, 0073, 0074 and 0075
The local VxVM Diskgroup named "DopeyDg", consists of four disks replicated to the remote host "Bashful".
1.] A VxVM volume named "vol01" is created on Veritas disk media (dm) name "r1-008C" (aka EMC SYMDEV "008C").
Dopey # vxassist -g DopeyDg make vol01 1g
Dopey # vxprint -qhtg DopeyDgdg DopeyDg default default 36000 1298306534.57.Dopey
dm r1-008C emc0_008c auto 65536 4058368 -
dm r1-008D emc0_008d auto 65536 4058368 -
dm r1-008E emc0_008e auto 65536 4058368 -
dm r1-008f emc0_008f auto 65536 4058368 -
v vol01 - ENABLED ACTIVE 2097152 SELECT - fsgen
pl vol01-01 vol01 ENABLED ACTIVE 2097152 CONCAT - RW
sd r1-008C-01 vol01-01 r1-008C 0 2097152 0 emc0_008c ENA
2.] File system is created on volume "vol01", and is mounted on mount-point "/vol01"
Dopey # mkfs -F vxfs /dev/vx/rdsk/DopeyDg/vol01 version 7 layout
2097152 sectors, 1048576 blocks of size 1024, log size 16384 blocks
largefiles supported
Dopey# mkdir /vol01
Dopey # mount -F vxfs /dev/vx/dsk/DopeyDg/vol01 /vol01
Dopey # cp /etc/hosts /vol01/
3.] The current replicated state is "synchronized" as shown by "symrdf query".
Dopey # symrdf -g DopeyDg queryDevice Group (DG) Name : DopeyDg
DG's Type : RDF1
DG's Symmetrix ID : 000290300822 (Microcode Version: 5773)
Remote Symmetrix ID : 000290301414 (Microcode Version: 5773)
RDF (RA) Group Number : 11 (0A)
Source (R1) View Target (R2) View MODES
-------------------------------- ------------------------ ----- ------------
ST LI ST
Standard A N A
Logical T R1 Inv R2 Inv K T R1 Inv R2 Inv RDF Pair
Device Dev E Tracks Tracks S Dev E Tracks Tracks MDA STATE
-------------------------------- -- ------------------------ ----- ------------
DEV08C 008C RW 0 0 RW 0072 WD 0 0 S.. Synchronized
DEV08D 008D RW 0 0 RW 0073 WD 0 0 S.. Synchronized
DEV08E 008E RW 0 0 RW 0074 WD 0 0 S.. Synchronized
DEV08F 008F RW 0 0 RW 0075 WD 0 0 S.. Synchronized
Total -------- -------- -------- --------
Track(s) 0 0 0 0
MB(s) 0.0 0.0 0.0 0.0
Legend for MODES:
M(ode of Operation): A = Async, S = Sync, E = Semi-sync, C = Adaptive Copy
D(omino) : X = Enabled, . = Disabled
A(daptive Copy) : D = Disk Mode, W = WP Mode, . = ACp off
4.] The VxVM disks at the remote site (Bashful in this instance) are write-disabled.
Remote:
Bashful # vxdisk -eo alldgs list | grep DopeyDgemc1_0072 auto:cdsdisk - (DopeyDg) online c1t5006048C536979A0d65s2 srdf-r2
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
Note: The remote copy of the diskgroup "DopeyDg" cannot be imported at this time.
Bashful # vxdg import DopeyDgVxVM vxdg ERROR V-5-1-10978 Disk group DopeyDg: import failed:
Disk is in use by another host
Attempting to force import the diskgroup on the remote host will result in the disks being marked by VxVM as "error".
Bashful # vxdg -Cf import DopeyDgVxVM vxdg ERROR V-5-1-10978 Disk group DopeyDg: import failed:
No valid disk found containing disk group
Bashful # vxdisk -eo alldgs list | grep r2
emc1_0072 auto - - error c1t5006048C536979A0d65s2 srdf-r2
emc1_0073 auto - - error c1t5006048C536979A0d66s2 srdf-r2
emc1_0074 auto - - error c1t5006048C536979A0d67s2 srdf-r2
emc1_0075 auto - - error c1t5006048C536979A0d68s2 srdf-r2
Run "vxdisk scandisks" to refresh the VxVM related content.
Bashful # vxdisk scandisks
Bashful # vxdisk -eo alldgs list | grep r2emc1_0072 auto:cdsdisk - (DopeyDg) online c1t5006048C536979A0d65s2 srdf-r2
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
5.] The "symrdg split" operation write enables both the R1 and R2 SRDF luns.
The EMC SRDF "rdf" link is suspended, whilst the R2 devices are write enabled.
Local:
Dopey # symrdf -g DopeyDg splitExecute an RDF 'Split' operation for device group 'DopeyDg' (y/[n]) ? y
An RDF 'Split' operation execution is in progress for device group 'DopeyDg'. Please wait...
Suspend RDF link(s).......................................Done.
Read/Write Enable device(s) on RA at target (R2)..........Done.
The RDF 'Split' operation successfully executed for device group 'DopeyDg'.
Dopey # symrdf -g DopeyDg queryDevice Group (DG) Name : DopeyDg
DG's Type : RDF1
DG's Symmetrix ID : 000290300822 (Microcode Version: 5773)
Remote Symmetrix ID : 000290301414 (Microcode Version: 5773)
RDF (RA) Group Number : 11 (0A)
Source (R1) View Target (R2) View MODES
-------------------------------- ------------------------ ----- ------------
ST LI ST
Standard A N A
Logical T R1 Inv R2 Inv K T R1 Inv R2 Inv RDF Pair
Device Dev E Tracks Tracks S Dev E Tracks Tracks MDA STATE
-------------------------------- -- ------------------------ ----- ------------
DEV08C 008C RW 0 0 NR 0072 RW 0 0 S.. Split
DEV08D 008D RW 0 0 NR 0073 RW 0 0 S.. Split
DEV08E 008E RW 0 0 NR 0074 RW 0 0 S.. Split
DEV08F 008F RW 0 0 NR 0075 RW 0 0 S.. Split
Total -------- -------- -------- --------
Track(s) 0 0 0 0
MB(s) 0.0 0.0 0.0 0.0
Legend for MODES:
M(ode of Operation): A = Async, S = Sync, E = Semi-sync, C = Adaptive Copy
D(omino) : X = Enabled, . = Disabled
A(daptive Copy) : D = Disk Mode, W = WP Mode, . = ACp off
6.] The SRDF "R2" devices for which are now in a split state can be imported using VxVM.
a.] Refresh VxVM.
Bashful # vxdisk scandisks
b.] Import the diskgroup using "-Cf" with the vxdg command.
Bashful# vxdg -Cf import DopeyDg
Bashful # vxdisk -eg DopeyDg listDEVICE TYPE DISK GROUP STATUS OS_NATIVE_NAME ATTR
emc1_0072 auto:cdsdisk r1-008C DopeyDg online c1t5006048C536979A0d65s2 srdf-r2
emc1_0073 auto:cdsdisk r1-008D DopeyDg online c1t5006048C536979A0d66s2 srdf-r2
emc1_0074 auto:cdsdisk r1-008E DopeyDg online c1t5006048C536979A0d67s2 srdf-r2
emc1_0075 auto:cdsdisk r1-008f DopeyDg online c1t5006048C536979A0d68s2 srdf-r2
c.] Recover the volume within the diskgroup "DopeyDg"
Bashful# vxrecover -g DopeyDg -bs
d.] Fsck and mount the filesystem for volume "vol01"
Bashful # fsck -F vxfs /dev/vx/rdsk/DopeyDg/vol01log replay in progress
replay complete - marking super-block as CLEAN
Bashful # mount -F vxfs /dev/vx/dsk/DopeyDg/vol01 /vol01
Bashful # df -k /vol01Filesystem kbytes used avail capacity Mounted on
/dev/vx/dsk/DopeyDg/vol01
1048576 17750 966407 2% /vol01
Bashful # ls /vol01hosts lost+found
Process complete.
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