Resolving server parameter errors when conducting File Import sessions

During File Import operations between VNX1/VNX2 and Unity systems, some parameter values need to be maintained within certain limits in order to guarantee successful and non-disruptive File Import operations.  The following example shows a parameter that is set differently on the VNX side than on the Unity side, and in this situation, the File Import create session fails:

Create VDM Import session..........................x Failed
Details
Failed: Server parameter error: {0}Search for kb000490660 in EMC knowledge base at https://support.emc.com. (Error Code:0x9000195)

This Knowledgebase article outlines the server parameter values that are checked during the File Import session create, and explains how to resolve mismatch issues.  The reason for maintaining an acceptable range of parameter values between VNX and Unity systems is to ensure that Host access is not disrupted during the File Import/migration process.  If parameter values are changed outside of the recommendations outlined below, then migration transparency to Host users cannot be guaranteed.

The following list contains the parameters that are checked during File Import operations between VNX and Unity.

nfs.transChecksum
Description:
Specifies whether the Data Mover supports Oracle Direct NFS (DNFS) for clients that use Oracle Database 11g with NFSv3. When support is enabled, the Data Mover ensures that each transaction carries a unique ID and avoids the possibility of conflicting IDs that result from the reuse of relinquished ports.
0 = Do not support DNFS.
1 = Support Oracle 11g DNFS clients that use NFSv3.
Value Range: 0 or 1
VNX1/2 default value: 0           
Unity default value: 0 
File Migration Pre-check Rule: VNX1/2 current value = Unity current value
Impact to File Migration if we omit this check: When VNX1/2 value is set to 1 and Unity value is 0, Oracle applications could lead to data corruption after migration cutover, in case of Oracle cluster failover. An IO after cluster failover could be considered as been already done when it was not the case.

nfs.v3xfersize
Description: Specifies the default transfer size for NFSv3 reads and writes.
Value Range: from 8192 to 1048576
VNX1/2 default value is based on the memory size of DM module
6G: 65536
8G/12G/16G: 131072
24G: 262144          
Unity default value:
Unity300: 65536
Unity400: 131072
Unity500: 131072
Unity600: 262144
File Migration Pre-check Rule: VNX1/2 current value <= Unity current value
Impact to File Migration if we omit this check:  It may cause client I/O error after migration cutover, which will not be solved until user re-mount, which the value in source VNX1/2 is larger than that in destination Unity array.

filesystem.rstchown
Description:
Sets restricted file ownership.
0 = Allow the owner of a file to change the file ownership or group ID to any other owner or group because chown and chgrp follow the less restrictive Portable Operating System Interface for Unix (POSIX) semantics.
1 = Allow only the superuser to change the owner of a file. The current owner can change the group ID only to a group to which the owner belongs. Note: This parameter applies to NFS, but not to CIFS.
Value Range: 0 or 1
VNX1/2 default value: 1           
Unity default value: 1 
File Migration Pre-check Rule: VNX1/2 current value = Unity current value
Impact to File Migration if we omit this check: In case the source VNX1/2 gets a value of 0 and destination Unity has 1 as value, application running with Id not root could get error, when they used to be able to change user/group ownership of file they have created.

quota.useQuotasInFsStat
Description:
Controls whether quotas are included when displaying file system free-space statistics to NFS clients that use the UNIX df -k command to view statistics.
0 = Exclude quotas when a disk quota verification is done by using df. The actual available space can be less than the "space available" shown in the command output.
1 = Include quotas. The df command run by a nonroot user reports only the space available to the user. This means the "space available" displays factors in the space that are preallotted to quota trees, users, and groups. rquota is not supported for tree quotas.
Value Range: 0 or 1
VNX1/2 default value: 0           
Unity default value: 0
File Migration Pre-check Rule: VNX1/2 current value = Unity current value
Impact to File Migration if we omit this check: When a NFS user is looking at available space on the exports he has access (through df command), he would see the full filesystem size which is larger than the amount of space he is able to use because of his user quota limit if the value of this parameter in VNX1/2 is 1 and in Unity is 0.
 
cvfs.virtualDirName
Description:
VVFS version 2 allows users to traverse mounted checkpoint from a hidden virtual directory. This parameter defines a user-specified virtual directory name. The actual directory name is the specified string preceded by a dot.
Example:
ckpt = Use .ckpt for the virtual directory name.
snapshot = Use .snapshot as the virtual directory name.
Note: Reboot the Data Mover for changes to take effect. 
Value Range: *
VNX1/2 default value: ckpt          
Unity default value: ckpt 
File Migration Pre-check Rule: VNX1/2 current value = Unity current value= ckpt 
Impact to File Migration if we omit this check: File Migration feature doesn t migrate the snapshots of a file system. Internally, the .ckpt is treated as the default virtual directory name and ignored during data copy. Use a different value in VNX1/2 could leads two problems:
   The real virtual directory data is migrated to destination array although it is useless and waste time.
   If  .ckpt  is used for other purpose, the data in that directory would be missed on destination after migration cutover.

Resolving Parameter Issues:
You can resolve parameter differences via any of the following three options:

• Modify the Source VNX parameter to an acceptable range for the Unity Import operation (server_param)
• Modify the Target Unity parameter to match the values located on the VNX Data Mover (VDM) [svc_param]
• Bypass the Parameter Checks when creating the File Import session in the GUI by unchecking the "Allow Comparison of Server Parameters" checkbox, or using the '-skipServerParamCheck' if creating an Import Session from UEMCLI

1.  Use  server_param  command to modify server parameters on the VNX system.  Refer to   Parameters Guide for VNX  for File  for more detail on how to modify Data Mover parameters on VNX.
2.  If you would rather modify the parameters on the destination Unity system, use the service tool  svc_param  to modify the appropriate parameter value.  Use svc_param -help to see the usage of this script.
3.  Use  -skipServerParamCheck  option during import session creation to skip parameter checking if using UEMCLI, or uncheck the "Allow Comparison of Server Parameters" checkbox in the GUI Import Session create wizard, on the 'Settings' page.
Note:  Bypassing parameter checking could result in Host disruption when the File Import sessions are being cutover to the Unity system, and in some cases, may require that the filesystems be remounted by the NFS Hosts.  Parameter checking is designed to ensure that 'NFS Transparency' (lack of disruption to Clients) is obtained with File Import operations.

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