http:\/\/vowe.net\/archives\/006448.html<\/p>\n
<\/p>\n
When a mirror is not a mirror
\nby Volker Weber<\/p>\n
Turn back the clock two years and imagine you want to run a web server for your small company, hosted in your ISP’s datacenter. You go and buy a DELL Poweredge pizza box, complete with two IDE drives. You install Windows on disk 1, make two partitions for system and data and then you tell Windows to mirror disk 1 to disk 2. Just in case one of the disks fails later on. What you don’t know yet is that IBM IC35L020AVER07 disks are not what you want in your server.<\/p>\n
Fast forward to Oct 23, 2005. Disk 1 dies. Server crashes. You buy two new disks, just because the other disk is also two years old now. Disks are cheap and server uptime is more important then saving a few bucks. What is the plan? You remove disk 1 and boot from disk 2. This is a mirror of disk 1, right?<\/p>\n
Wrong.<\/p>\n
Disk 1 has a MBR, one DELL service partition and two partitions you built: system and data. However, you find out that disk 2 only has three partitions. All of them “dynamic volumes”. There is no boot record, so the disk won’t boot at all. What Microsoft is not telling you:<\/p>\n
Keep in mind that you cannot boot to a drive that contains only dynamic volumes. If you mirror your system drive, be sure to partition the drive first and then delete the partition and mirror it. This creates a bootable partition in the MBR.<\/p>\n
Nobody told you this. Windows conveniently built a mirror that won’t work. Neat, eh?<\/p>\n
The trouble does not stop here. You create a BartPE disk, a live Windows Boot CD, admin’s best friend. But you won’t be able to see disk 2 when disk 1 is not present. You first have to use Diskpart to break the mirror. This ain’t easy since Diskpart insists on seeing the other disk. Would you dare to break the mirror before having saved the most valuable data from the disk?<\/p>\n
Well, normally you would just ignore Windows, whip out your handy Linux boot disk and mount the NTFS drives to get to the data. Not with dynamic volumes though:<\/p>\n
If a partition table entry of type 0x42 is present in the legacy partition table, then W2K ignores the legacy partition table and uses a proprietary partition table and a proprietary partitioning scheme (LDM or DDM). As the Microsoft KnowledgeBase writes: Pure dynamic disks (those not containing any hard-linked partitions) have only a single partition table entry (type 42) to define the entire disk. Dynamic disks store their volume configuration in a database located in a 1-MB private region at the end of each dynamic disk.<\/p>\n
Tune in tomorrow when the story continues.<\/p>\n","protected":false},"excerpt":{"rendered":"
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