Luns that are greater than 1TB are susceptible to data corruption during upgrade to 5.1SP1 and above

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Article ID: 100027185

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Description

Error Message

There are no visible errors generated .  The (silent) data block corruption is detectable only by applications like dbverify etc.

Corruption is confirmed when the following pattern is found in the data region of the disk.

cyl alt 2 hd sec

 

Cause

The Cross-Platform Data Sharing (CDS) disk maintains a SUN VTOC in the zeroth block and a backup label at the end of the disk. The VTOC maintains the disk geometry information like number of cylinders, tracks and sectors per track. The backup label is the duplicate of VTOC and the backup label location is determined from VTOC contents. As part of resize, VTOC is not updated to the new size, which results in the wrong calculation of the backup label location. If the wrongly calculated backup label location falls in the public data region rather than the end of the disk as designed, data corruption occurs.

 Two issues that could lead to data block corruption.

 1)  When upgrading to versions 5.1SP1RP1  through 5.1SP1RP2P1 corruption can happen at the calculated SMI(vtoc) size

2)  When upgrading to 5.1SP1RP2P2 or greater corruption can happen at the calculated 1TB marker.

Resolution

An updated installer script is available. It alters the installation script so that it detects disks that are susceptible to corruption before the VxVM daemons are started.

1. Before installing Service Pack 1 (SP1), or any roll-up packs (RP) for SP1, download the updated Common Product Installer (CPI) script.

Download links for the updated CPI:
 
Hotfix 13 for 5.1 SP1 
 
Hotfix 1 for 5.1 SP1 RP4
 
2. While installing SP1, or RP, use the "-require" switch to force the installer
to use the updated CP:
 
To install SP1:    
./installer -require -nostart
 
To install an RP:
./installrp -require  -nostart
 

Applies To

PLATFORMS: AIX, HPUX and Linux only.

AIX and HP are more likely to run into this problem as they allow cdsdisk with SMI labels for luns that are greater than 2TB in size.
 
If luns initialized in AIX and HP are greater that 1TB but under 2TB they must be a defective disk.
 
Linux does not allow luns to be greater than 2TB with a standard SMI label so they must be a defective disk.

(1)     cdsdisk was initialized with SMI (aka VTOC) label on a disk greater than 1 TB on a release prior to 51sp1.

(2)     Applicable only for HP-UX or AIX or Linux.  Not applicable to Solaris.

(3)     Disk size must be at least 1 TB

(4)     (public region offset + public region size) > s2 partition size in the sector 0 VTOC label.

 

Issue/Introduction

         Luns over 1TB in size in Volume Manager (VxVM) version 5.0.x could be susceptible to data corruption when upgrading to 5.1SP1 or greater.  The corruption can occur only if the following four conditions are met : 1)       Must be initialized in VxVM versions 5.0.x               a.        This will place a standard SMI label on the LUN
              b.       SMI(vtoc) label will be placed in block 0 of the lun
 
2)       Must be greater than 1TB
 
              a.        If LUN is greater than 2TB it will be a defective disk
 
3)       Must be a defective disk
 
             a.        A defective disk is defined as:
 
                                    i.      Number of cylinders is more than 65535 (2^16)
4)     (public region offset + public region size )  must be greater than calculated SMI(vtoc)  label size  
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