Replication with SFW/VVR 5.1 SP2 where system only has harddisk0

[stookler]

A customer has a Windows 2003 system with a single internal hard disk (harddisk0).  There is no external storage attached to this system.  SFW & VVR 5.1 SP2 have been installed on this system.  There are two volumes on harddisk0........the volume for the C: drive, and a second volume for the D: drive.

The customer is asking if this single hard disk (harddisk0) can be placed into a Veritas dynamic disk group, so that VVR can be used to replicate the data on the D: drive volume.  We can shrink the D: drive to make room for the SRL log volume.

I know this isn't recommended as a best practice, but I want to check with the Symantec engineers, to see if we can, in fact, put the harddisk0 (containing the C: drive) into a dynamic disk group, and replicate the D: drive, without adding another physical hard disk (harddisk1) to the system.

I've read through the SFW and VVR documentation, and there isn't anything specific about whether or not you can put harddisk0 into a Veritas dynamic disk group.

[Michael_Black · Accepted solution]

It is possible to add the system disk to a dynamic disk group. As you mentioned, this is not usually recommended. When you add the system drive to a Veritas dynamic disk group, it will "encapsulate" the volume into the updated version.  If Storage Foundation is ever uninstalled, the system drive will be unreadable to the native Windows disk drivers.

Additionally, having the SRL located on the same disk as the replicated volume is not recommended for performance reasons.

[RiaanBadenhorst]

Hi,

I'm not certain it will work. Haven't tested it for a while though. I do recall that in previous versions, when you encapsulate the O/S it gets placed under SF control, but the diskgroup that contains the O/S doesn't have access to all the feature (snapshots, flashsnap, etc). I've not confirmed this with VVR but I'm almost sure it won't allow you to place the Primary Diskroup containing C into a RDS.

I would investigate this further if I was you.

[Wally_Heim]

Hi Stooker,

Converting the system disk to dynamic is not a problem.  SFW will only allow disks that contain the system and/or boot partitions to be included in Windows Compatible disk groups - not native SFW dynamic disk groups.  This means that even is SFW is uninstalled the system and/or boot partitions will be accessible by Windows - maning the server will still boot.

the down side of this is as Raan mentioned.  VVR is an advanced feature of SFW and it requires a SFW dynamic disk group - not a windows compatible disk group.  The end result is that you can not replicate any partitions/volumes that are on the same physical disk as the system/boot partitions.

You can make the is work by using another physical drive in the server.  But if that is not an option than VVR will not work for you where you only have a single disk that holds the system partition and the partition to be mirrored.

Thanks,

Wally

[mikebounds]

Is Harddisk0 a physical disk or a LUN provided by some RAID software.  I have seen a few Windows servers where there are 2 disks in the server which are mirrored to present one LUN to the host and where this is done you can sometimes get the RAID software to present two mirrored LUNs to the host.

This would probably involve a reload of the O/S, unless the RAID software supports shrinking a LUN.

Easiest option is to just add a disk to the server, as Wally says, and a cheap disk will give you better performance than sharing O/S disk, as one physical disk containing O/S, page file, application and SRL is going to give quite bad performance.

Mike