Storage Foundation 7.4.1 Administrator's Guide - Linux

To migrate to thin provisioning

1. Check if the SmartMove feature is enabled.

   # vxdefault list
   KEYWORD                        CURRENT-VALUE   DEFAULT-VALUE  
   usefssmartmove                 all             all       
   ...

   If the output shows that the current value is none, configure SmartMove for all disks or thin disks.

   See Configuring SmartMove .

2. Add the new, thin LUNs to the existing disk group. Enter the following commands:

   # vxdisksetup -i da_name
   # vxdg -g datadg adddisk da_name

   where da_name is the disk access name in VxVM.

3. To identify LUNs with the thinonly or thinrclm attributes, enter:

   # vxdisk -o thin list

4. Add the new, thin LUNs as a new plex to the volume. On a thin LUN, when you create a mirrored volume or add a mirror to an existing LUN, VxVM creates a Data Change Object (DCO) by default. The DCO helps prevent the thin LUN from becoming thick, by eliminating the need for full resynchronization of the mirror.

   NOTE: The VxFS file system must be mounted to get the benefits of the SmartMove feature.

   The following methods are available to add the LUNs:

   • Use the default settings for the vxassist command:

     # vxassist -g datadg mirror datavol da_name

   • Specify the vxassist command options for faster completion. The -b option copies blocks in the background. The following command improves I/O throughput:

     # vxassist -b -oiosize=1m -t thinmig -g datadg mirror \
       datavol da_name

     To view the status of the command, use the vxtask command:

     # vxtask list
     TASKID PTID TYPE/STATE    PCT   PROGRESS
     211         ATCOPY/R 10.64% 0/20971520/2232320 PLXATT vol1 vol1-02 xivdg smartmove
     212         ATCOPY/R 09.88% 0/20971520/2072576 PLXATT vol1 vol1-03 xivdg smartmove
     219         ATCOPY/R 00.27% 0/20971520/57344 PLXATT vol1 vol1-04 xivdg smartmove

     # vxtask monitor 211  
     TASKID PTID TYPE/STATE    PCT   PROGRESS
     211         ATCOPY/R 50.00% 0/20971520/10485760 PLXATT vol1 vol1-02 xivdg smartmove
     211         ATCOPY/R 50.02% 0/20971520/10489856 PLXATT vol1 vol1-02 xivdg smartmove
     211         ATCOPY/R 50.04% 0/20971520/10493952 PLXATT vol1 vol1-02 xivdg smartmove
     211         ATCOPY/R 50.06% 0/20971520/10498048 PLXATT vol1 vol1-02 xivdg smartmove
     211         ATCOPY/R 50.08% 0/20971520/10502144 PLXATT vol1 vol1-02 xivdg smartmove
     211         ATCOPY/R 50.10% 0/20971520/10506240 PLXATT vol1 vol1-02 xivdg smartmove

   • Specify the vxassist command options to reduce the effect on system performance. The following command takes longer to complete:

     # vxassist -oslow -g datadg mirror datavol da_name

5. Optionally, test the performance of the new LUNs before removing the old LUNs.

   To test the performance, use the following steps:

   • Determine which plex corresponds to the thin LUNs:

     # vxprint -g datadg

     TY NAME         	     ASSOC   	       KSTATE   LENGTH     PLOFFS  STATE     TUTIL0 PUTIL0
     dg datadg       	     datadg      	   -        -          -       -         -       -
     dm THINARRAY0_02      THINARRAY0_02   -      	 83886080   -       -         -       -
     dm STDARRAY1_01	      STDARRAY1_01    -  	     41943040   -       -OHOTUSE  -       -
     
     v  datavol      	     fsgen        	  ENABLED 	41943040   -       ACTIVE    -       -
     pl datavol-01   	     datavol      	  ENABLED 	41943040   -       ACTIVE    -       -
     sd STDARRAY1_01-01    datavol-01   	  ENABLED 	41943040   0       -         -       -
     pl datavol-02   	     datavol      	  ENABLED 	41943040   -       ACTIVE    -       -
     sd THINARRAY0_02-01   datavol-02   	  ENABLED 	41943040   0       -         -       -

     The example output indicates that the thin LUN corresponds to plex datavol-02.

   • Direct all reads to come from those LUNs:

     # vxvol -g datadg rdpol prefer datavol datavol-02

6. Remove the original non-thin LUNs.

   Note:

   The ! character is a special character in some shells. This example shows how to escape it in a bash shell.

   # vxassist -g datadg remove mirror datavol \!STDARRAY1_01
   # vxdg -g datadg rmdisk STDARRAY1_01
   # vxdisk rm STDARRAY1_01

7. Grow the file system and volume to use all of the larger thin LUN:

   # vxresize -g datadg -x datavol 40g da_name