topic Re: Post P2V Mbralign Problem in VMware Solutions Discussions

Post P2V Mbralign Problem

__CHRIS_CYRE_19529 — Thu, 05 Jun 2025 07:28:28 GMT

We are in the middle of doing P2V conversions here at the bank. They have all P2V'ed just fine. Then we go to mbralign the vmdk files and some have been OK others have come back with warnings.....

Backup hidden did not match primary. No change was made to backup. This usually indicates a failure in the mbralign process or data corruption. You should consider reverting this process (run the script again and choose yes to the "Shall I restore" questoin).

It says that twice then asks the question.

The servers that have worked have multiple partitions or at least a c and a e drive. All reside on Windows drive 0. The ones that do not work have the same setup. A C and an E drive on drive 0. I'm not sure of the mbralign version that is on the vmhost as a vendor put it on. I'm trying to find out now. In the meantime I can't find anything about this error out there and I find it hard to believe I'm the only one who's ever seen this. Thanks

Re: Post P2V Mbralign Problem

amiller_1 — Sun, 10 May 2009 02:04:56 GMT

Let me see if I can ask someone who might know the answer to this...

To see the version of mbralign just run "mbralign --help" to see it....if you're not running the latest version (1.4), I'd try upgrading to that regardless.

Re: Post P2V Mbralign Problem

forgette — Mon, 11 May 2009 13:47:34 GMT

Andrew is correct, 'mbralign --help' should show the version. The latest version is 1.40090416.

The first thing you'll want to do is grab the latest version of mbralign (if you don't have it). If this doesn't clear up the problem, we can make arrangements to get the debug output from you.

Here is a description of what is going on:
When mbralign detects a partition that contains an NTFS filesystem (partition type 0x07), it makes adjustments to the NTFS boot sector of that filesystem. A second copy of this metadata is kept in the last 512 bytes of the filesystem as a backup. This backup was very important in the days of physical disk systems because a single sector error (at the right location) could render the filesystem unusable for boot. Today, this is less important especially in the case of a virtual hard drive (vmdk file) on a enterprise storage array.

Both versions of mbralign read the backup boot sector before making adjustments to it. In mbralign 1.2, if the backup didn't match the original, the warning/error you received is displayed. The 1.40090416 version handles this better in that it compares the backup to the original backup (not the original). If it doesn't match in this case (much lower likelihood), you'd get the error as well. In this case, the debug information (--debug) can be used to determine if its safe to use the resulting file.