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 Data were lost from the changed and subsequent partitions. Now FW 4.x allow the partition size modification or deletion, letting the  subsequent partitions unchanged

This document shows how the partition modifications operate with FW 4.x

Deletion a partition

The following example shows a condition under which data loss  occur  only on the modified  and the upper partitions. This example assumes that the logical drive is partitioned as outlined below. The partition information is displayed from the telnet interface into the array.

This example also assumes the following logical drive and partition configuration. The output below is displayed by using the  sccli  command.

sccli> show logical

LD    LD-ID        Size  Assigned  Type   Disks Spare  Failed Status

------------------------------------------------------------------------

ld0   3EDCEA31  11.72GB  Primary   RAID5  5     0      0      Good

                         Write-Policy Default          StripeSize 128KB

sccli> show part

LD/LV    ID-Partition        Size

-------------------------------------

ld0-00   3EDCEA31-00       1000MB

ld0-01   3EDCEA31-01       1.46GB

ld0-02   3EDCEA31-02       1.95GB

ld0-03   3EDCEA31-03       2.44GB

ld0-04   3EDCEA31-04       4.88GB

Based on the above configuration, if partition 2 is deleted, all the data from Logical drive are  lost. The on-screen prompt which is displayed before deleting partition 2 would be as follows.

       _______________________________________
| This operation will result in the     |
| LOSS OF ALL DATA on the Logical Drive!|
|                                       |
|      Partition Logical Drive          |
|                                       |
|         Yes            No             |
|_______________________________________|

This message could easily be interpreted as meaning that only the data from partition 2 and 1  will be lost.

The reason for that is that now FW 4.xx doesn't move the freed space to the last partition, but add the freed space to the upper  partition. That result to a larger  upper  partition,   but   most of all, the  lower partitions are unchanged and  hence the data are still available. Only the  lun numbering  is changed.

The following partition table shows the partition offsets after the deletion of partition 2.

sccli> show part

LD/LV    ID-Partition        Size

-------------------------------------

ld0-00   3EDCEA31-00       1000MB

ld0-01   3EDCEA31-01       3.42GB

ld0-02   3EDCEA31-02       2.44GB

ld0-03   3EDCEA31-03       4.88GB

A side-effect of the LUN numbering modification   is that all  LUN mappings need to be removed before modification  for the changed and subsequent partitions. Then mappings will need to be redefined after the partition deletion has been completed.

Important - Due to the   new behavior described above, it is imperative that   at least data  from  modified and the upper  partitions   be backed up , but it is recommended to back up  all LD to avoid  the  consequences of the partition mishandling. Once the partition changes have been made, redefine the LUN mappings, and then restore the logical drive data from the backup.

Partition shrink

 I take the same LD partitioning,  but instead of  deleting  the partition #2, I l shrink it to the minimum size 1MB

sccli> show logical

LD    LD-ID        Size  Assigned  Type   Disks Spare  Failed Status

------------------------------------------------------------------------

ld0   3EDCEA31  11.72GB  Primary   RAID5  5     0      0      Good

                         Write-Policy Default          StripeSize 128KB

sccli> show part

LD/LV    ID-Partition        Size

-------------------------------------

ld0-00   3EDCEA31-00       1000MB

ld0-01   3EDCEA31-01       1.46GB

ld0-02   3EDCEA31-02       1.95GB

ld0-03   3EDCEA31-03       2.44GB

ld0-04   3EDCEA31-04       4.88GB

Based on the above configuration, if partition 2 is shrunk, all the data from Logical drive are  lost. The on-screen prompt which is displayed before deleting partition 2 would be as follows.

  _______________________________________
| This operation will result in the     |
| LOSS OF ALL DATA on the Logical Drive!|
|                                       |
|      Partition Logical Drive          |
|                                       |
|         Yes            No             |
|_______________________________________|

sccli> show part

LD/LV    ID-Partition        Size

-------------------------------------

ld0-00   3EDCEA31-00       1000MB

ld0-01   3EDCEA31-01       1.46GB

ld0-02   3EDCEA31-02          1MB

ld0-03   3EDCEA31-03       1.95GB

ld0-04   3EDCEA31-04       2.44GB

ld0-05   3EDCEA31-05       4.88GB

Here when size is modified , the FW behavior is different than  when partition is deleted. FW doesn't add the deleted MB to the upper partition , but create a new partition with the deleted MB just after the shrunk partition and modify  the partition number of the unchanged partitions.

important - Due to the   new behavior described above, it is imperative that   at least data  from  modified  partitions   be backed up , but it is recommended to back up  all LD to avoid  the  consequences of the partition mishandling. Once the partition changes have been made, redefine the LUN mappings, and then restore the logical drive data from the backup.

Currently I can tell whether the different FW behaviors between
the partition deletion and modification is normal or a bug.

From the 817-3711-14/ch06_logdrives.html#26345 documentation

 Deleting a Logical Drive Partition

When you delete a partition on a logical
drive, all of the capacity of the deleted partition is added to the
remaining partition with the highest partition number. For example,
if a logical drive contains partitions 0 through 3 and you delete
partition 3, all of the capacity of partition 3 is added to
partition 2.

 I will follow this  to clarify it with PDE.

Because of the lun numbering shift  when modification or
deletion is done  

ALL luns must be unmapped

.
Currently a  warning message appears only on  the
selected lun  if it  is mapped ; see Bug ID: 6365977

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