Creating Thin Image Advanced pairs

When you create a pair, you specify a pool, a P-VOL, and an S-VOL to be used for the pair. You can also create a pair without specifying an S-VOL. If you specify an S-VOL when you create a Thin Image Advanced pair, the S-VOL must satisfy the following conditions:

• The S-VOL and the P-VOL must be the same size.
• The S-VOL must belong to the same pool as the P-VOL.

Requirements:

• You cannot use the paircreate command to create pairs.
• You can specify an MU number when you create a pair. If you do not specify an MU number, an MU number is automatically assigned in the order of 3 to 1,023, followed by 0 to 2. Note that ShadowImage uses MU numbers 0 to 2. If Thin Image Advanced is already using MU numbers 0 to 2, Thin Image Advanced volumes cannot be shared with ShadowImage volumes.
• The value of the T10 PI attribute must be the same for the P-VOL and S-VOL.
• A Thin Image Advanced pair cannot be created when the used pool capacity exceeds the warning threshold. In this case, increase the pool capacity first, and then create the pair.
• To prevent the Thin Image Advanced pairs from being suspended ("PSUE" status), do not create Thin Image Advanced pairs while you are shutting down the storage system.
• When only the P-VOL capacity of a Thin Image Advanced pair has been expanded, a cascaded pair cannot be created. Create the cascaded pair after expanding all of the volume capacity used in the pairs.
• You cannot create a pair using volumes in the SMPP status (the pair is being deleted). Run the raidcom get snapshot command with the -key detail option to display a list of pairs. Check that the pair status changes from SMPP to SMPL and the volumes in the pair to be deleted disappear from the list. When the volumes are no longer in the list, use them to create a Thin Image Advanced pair.
• If no Thin Image pair exists in a pool and only a Thin Image Advanced pair in the PAIR status or a Thin Image Advanced pair without differential data exists in the pool, Device Manager - Storage Navigator or CCI displays the maximum value it can display for the Snapshot Efficiency Ratio (SNAPSHOT_EFF_R). For example, if you create a Thin Image Advanced pair for the first time in a pool containing no Thin Image pairs and then you immediately reference the Snapshot Efficiency Ratio, Device Manager - Storage Navigator or CCI displays the maximum displayable value of the rate. Device Manager - Storage Navigator and CCI can display the following maximum values for the Snapshot Efficiency Ratio:
  • HDvM - SN: 99999999999999.99
  • CCI: 92233720368547758.07

    (92233720368547758.07 is one hundredth of 0x7FFFFFFFFFFFFFFF (hexadecimal value).)

The following examples create a pair and add the Thin Image Advanced pair to the consistency group by specifying the following:

• P-VOL, S-VOL, and pool
• P-VOL and pool
• MU number

The examples use LDEV number 10:10 for the P-VOL, LDEV number 20:20 for the S-VOL, SnapPool00 for the pool in the db1 snapshot group. The MU number in the example is "4".

The final example adds multiple pairs to one consistency group. To add multiple pairs to one consistency group, repeat the command for the target consistency group (snapshot group) for the number of pairs you want to add. When you add subsequent new pairs to a consistency group, if the consistency group contains a pair that is already created with CTG specified in the -snap_mode option, you can omit specifying CTG for the -snap_mode option.

raidcom add snapshot -ldev_id 0x1010 0x2020 -pool SnapPool00
-snapshotgroup db1 -snap_mode cascade CTG

raidcom add snapshot -ldev_id 0x1010 -pool SnapPool00
-snapshotgroup db1 -snap_mode cascade CTG

raidcom add snapshot -ldev_id 0x1010 -pool SnapPool00
-snapshotgroup db1 -snap_mode cascade CTG -mirror_id 4

raidcom add snapshot -snapshotgroup row1 -pool 2 -ldev_id 900 
-snap_mode cascade CTG

raidcom add snapshot -snapshotgroup row1 -pool 2 -ldev_id 901 
-snap_mode cascade

raidcom get snapshot -snapshotgroup row1 -key detail
SnapShot_name P/S   STAT Serial# LDEV# MU# P-LDEV# PID % MODE SPLT-TIME
row1          P-VOL PAIR  500079   900   3       -   2 - G--A -
row1          P-VOL PAIR  500079   901   3       -   2 - G--A -
SLU C_LDEV# P R
N         - N D
N         - N D