Expanding DP-VOL capacity used in a Thin Image pair

Thin Image User Guide

Version

9.8.6

Audience

anonymous

Part Number

MK-98RD9020-16

You can expand the capacity of a DP-VOL used only as a Thin Image pair volume. If you want to expand the DP-VOL capacity when the HTI pair shares volumes with other replication software, see the User Guide for that replication software.

A V-Vol to be expanded is not an external volume.
The LDEV format is being performed on a V-Vol to be expanded.
A pool containing a V-Vol to be expanded meets any of the following conditions:
- Normal condition
- The used capacity of the pool does not exceed the threshold.
- The pool is not being shrunk.
A V-Vol to be expanded is a volume created on the storage systems described in Expanding DP-VOL capacity while keeping the pair status.
A V-Vol to be expanded is not used in a pair with the clone attribute.
The following numbers required after the expansion do not exceed the maximum number allowed on the storage system:
- The snapshot estimated manageable capacity
- The number of cache management devices
- The subscription limit of the V-VOL capacity

Calculating the snapshot estimated manageable capacity, the number of cache management devices, and the subscription limit of the V-VOL capacity

Snapshot estimated manageable capacity required for expanding the Thin Image volume capacity
To expand the capacity of a Thin Image root volume, verify that the snapshot estimated manageable capacity is available. Calculate the snapshot estimated manageable capacity required for expanding the capacity of a Thin Image root volume using the following formulas:
```
Snapshot-estimated-manageable-capacity-for-root-volume-expansion = Snapshot-estimated-manageable-capacity-after-root-volume-expansion - Snapshot-estimated-manageable-capacity-before-root-volume-expansion
```
```
Snapshot-estimated-manageable-capacity = (Root-volume-capacity [TB] / 2.6 [TB]) x 3,024 [GB] + (168 [GB] x 2(consumed-shared-memory [GB]))
```
Expanding the volumes other than a root volume does not consume the snapshot estimated manageable capacity. You can check the snapshot estimated manageable capacity in the Local Replication window.
The number of cache management devices required for expanding the Thin Image volume capacity.
To expand the capacity of a Thin Image root volume, verify that the cache management devices are available. Calculate the maximum number of cache management devices required for expanding the capacity of a Thin Image root volume using the following formula:
```
number-of-cache-management-devices-for-root-volume-expansion = ceiling ((Root-volume-capacity-after-expansion [TB] / 2.6 [TB])) - ceiling ((Root-volume-capacity-before-expansion [TB] / 2.6 [TB]))
```
In the example, 'ceiling' refers to rounding up the value enclosed in parenthesis ( ) to the next integer. Expanding the volumes other than a root volume does not consume the cache management devices.
The subscription limit of the V-VOL capacity in a DP pool required for expanding the Thin Image volume capacity.
To expand the capacity of a Thin Image root volume, verify that the capacity after the expansion does not exceed the subscription limit of the V-VOL capacity contained in a DP pool.

Calculate the V-VOL capacity to be added by expanding the capacity of a Thin Image root volume using the following formulas:
```
V-VOL-capacity-added-by-root-volume-expansion = Thin-Image-pair-capacity-calculated-based-on- root-volume-capacity-after-expansion - Thin-Image-pair-capacity-calculated-based-on-root-volume-capacity-before-expansion
```
```
Thin-Image-pair-capacity = Σ ceiling ((Root-volume-capacity [MB] × number-of-pairs* × 2/ 42 [MB])) × 42 [MB] + Σ ceiling ((Root-volume-capacity [MB] × number-of-pairs* × 2/ 2,921,688 [MB])) × 175,434 [MB]
```
* number-of-pairs: The allocated pages are not released if you delete some pairs. Therefore, use the maximum number of HTI pairs to be created in the applicable snapshot tree as number-of-pairs instead of the number of pairs currently created in the applicable snapshot tree.

Round up the value enclosed in ceiling ( ) to the next integer.

Expanding the volumes other than a root volume does not add the V-VOL capacity contained in a DP pool in Thin Image.

Verify that all of the volumes used in HTI meet the prerequisites.
If only one volume capacity used in an HTI pair can be expanded, while the other cannot be expanded, the resync operation of the HTI pair cannot be performed after the expansion because the capacity of both the volumes is not the same.

If the resync operation of the HTI pair cannot be performed, complete the procedure in (1) Recovery procedure from failure if one volume capacity used in Thin Image pair cannot be expanded.
Verify the pair statuses of the HTI pairs.
The HTI pair volume capacity can be expanded when the HTI pairs are in the PAIR or PSUS status. Verify the current pair statuses of the HTI pairs. If the pair statuses are not PAIR or PSUS, perform the pair operations, and then make sure that the pair statuses change to PAIR or PSUS.
Note: If the statuses remain PSUE or change to PSUE, this indicates an error condition.
If the cascade attribute of the volume to be expanded is enabled, proceed to the next step. If the cascade attribute of the volume to be expanded is disabled, release the assignment of the S-VOL to snapshot data of the HTI pair.
If the multiple S-VOLs are included, release the assignment of the S-VOL to snapshot data for each volume. Skip this operation if the assignment of the S-VOL to snapshot data has already been released.
Expand the P-VOL capacity used in the HTI pair.
- When using CCI, add the -request_id auto option to the raidcom extend ldev command to specify the asynchronous command processing. For example, to expand the capacity of LDEV#44:44 by 10GB:
```
raidcom extend ldev -ldev_id 0x4444 -capacity 10G –request_id auto -IH1
```
- When using HDvM - SN, expand the capacity in the Expand V-VOLs window.
Verify that expanding the P-VOL capacity used in the HTI pair is complete.
- When using CCI, use the raidcom get command_status command to verify that the raidcom extend ldev command processing is complete, and then verify that the LDEV capacity is correct using the raidcom get ldev command. For example:
```
raidcom get command_status -IH1
raidcom get ldev -ldev_id 0x4444 -fx -IH1
```
- When using HDvM - SN, select Logical devices from the Storage Systems tree, and then display the LDEV tab. Verify that the capacity with the target LDEV number is correct.
If the cascade attribute of the volume to be expanded is disabled, proceed to step 8. If the cascade attribute of the volume to be expanded is enabled, expand the S-VOL capacity of the HTI pair in the same way as the P-VOL capacity.
If the S-VOL capacity used in the HTI pair cannot be expanded, perform the procedure in (1) Recovery procedure from failure if one volume capacity used in Thin Image pair cannot be expanded.
Verify that expanding the S-VOL capacity used in the HTI pair is complete in the same way as the P-VOL capacity
If the cascade attribute of the volume to be expanded is enabled, proceed to step 9.
If the cascade attribute of the volume to be expanded is disabled, prepare the LDEV with the same capacity as that after the expansion, and then assign the LDEV as the S-VOL to snapshot data of the HTI pair.

If the multiple HTI pairs are included, assign the S-VOL to snapshot data of each HTI pair. Skip this operation if the assignment of the S-VOL to snapshot data is not required.
Verify that the volume capacity used in the HTI pair is not being expanded.
- When using CCI, check if the P column in the pairdisplay command or raidcom get snapshot command displays N. Following are examples of each command:
```
# pairdisplay -g ti -fxce -IM3
Group   PairVol(L/R) (Port#,TID, LU-M) ,Seq#,LDEV#.P/S,Status,   % ,P-LDEV# M CTG CM EM       E-Seq# E-LDEV# DM P

ti      ti00(L)     (CL1-C-0,28,   0-0 )500003  2000.P-VOL PAIR,  100    3000 -   -  S  -            -       - -  N
ti      ti00(R)     (CL1-C-0,28,   1-0 )500003  3000.S-VOL PAIR,  100    2000 -   -  S  -            -       - -  N
```
```
# raidcom get snapshot -ldev_id 0x1000 -key opt -fx SnapShot_name P/S STAT Serial# LDEV# MU# PLDEV#
PID % MODE SPLT-TIME SLU C_LDEV# P
ti P-VOL PAIR 500001 1000 3 1100 5 100 ---- - - - N
```
  The P column displays the status of the volume capacity that is being expanded:
  - N: The volume capacity is not being expanded.
  - E: The volume capacity is being expanded.
  This status has been displayed for a while (30 seconds or so) after the expansion of the P-VOL or the S-VOL capacity is complete, and then this status is changed to N.
- When using HDvM - SN, in the Local Replication window, select a P-VOL containing a volume to be expanded in the TI Root Volumes tab, and then click Operate TI Pairs. Check if the Processing Status field in the TI Pairs window is blank. (Expanding displays when the volume capacity is being expanded.) If the volume capacity is being expanded, wait until the expansion is complete, and then verify the status.