Flexible Storage Sharing (FSS): Private Disk Groups are exported (mapped) to clustered nodes

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Article ID: 100033968

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Cause


 The user may wish to create Private disk groups in an FSS clustered environment, i.e. share local application binaries.

Figure 2.0


FSS-Localdg-Example

The user has created local disk groups with the same name on two different servers connected in the same FSS environment.

When deporting & importing the Private disk group, disks which have the same disk group name, the disk(s) are automatically mapped to the other node(s) in the cluster.

Where disk groups have the same name, vxconfigd selects the disk which has the newest creation time or disk group id (DGID).
The on-disk update timestamp can also be a factor.
 
Note: To prevent corruption, we don’t want the remote devices with the same disk group names being mapped to the clustered nodes.

When the disks are mapped to an unwanted server in the cluster, it is possible that the incorrect disk group image is selected during the import process.

Potentially, resulting in data corruption. Data written to wrong disk group image.

Resolution

Flexible Storage Sharing (FSS) has been enhanced to ensure Private disk groups are ONLY visible to the local server.

By the local disks no longer being visible to other nodes in the cluster. This ensures the local server will always import its required Private disk group image.

Figure 3.0

User-added image
Note: The enhanced FSS functionality will no longer remotely map Private (local) disk groups to other clustered nodes.
 
The disks are prefixed with the hostprefix.

Private Hot-fix

VxVM Private Hot-fix 7.2.0.004 is available for Linux, and will be ported across all platforms:
Solaris Sparc, AIX and HP-UX.


Process:

Deport all VxVM Disk Groups
Stop VCS
Apply the Private Hot-fix
Start vxconfigd and VCS on all nodes (where possible reboot each server)

 If you require this fix, please contact the Veritas Technical Support team.
 

Issue/Introduction

Flexible Storage Sharing (FSS) is built into the core components of InfoScale Storage and seamlessly combines shared and direct-attached storage under a common storage virtualization solution.
Direct-Attached-Storage (DAS) is simply digital storage that is directly attached to a server.

Figure 1.0

What is FSS? Visual Diagram
The Volume Manager daemon ”vxconfigd” gathers disk information. When vxconfigd imports a disk group, all the disks belonging to it are automatically mapped (exported).

This is done to increase the chances of importing the disk group.

Since we are exporting all disks in the disk group, disks which belong to the same disk group name, can be incorrectly mapped to other (unwanted) nodes in the cluster.

IMPACT:
This can result in the wrong disk being selected during the import phase. This can result in potential data corruption.

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