7.5 Shared Disk.
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It is managed disk using Mantech Volume Lock(MVL) bundled in MCCS.
Within a cluster, the application may be store the data on shared disk when it is equipped.
MVL attach the file system on shared disk to the only active server and lock to the standby server to prevent file system corruption. When managed as mentioned above, shared disk is defined as the drive letter.
A shared disk agent of the MCCS manages the lock/un-lock of the disk and monitors volume is read/writable state through communication with the MVL driver.
Table of Contents
Introduction to the MVL Driver
Mantech Volume Lock (MVL) is a kernel drive which provides the function of managing the shared disk for Windows OS.
MVL locks access to the shared disk resource. You cannot access the volume of shared disk before it unlocks access. Only a node allow to access to the shared disk resource.
MVL can be managed in volume unit and partition unit of Window but it is not recommended. But it is recommended to use volume unit management.
It supports both GPT disk and MBR disk, and for file system, it supports NTFS only.
MVL Installation and Removal
MVL can enable load / unload driver and activate without the need to reboot the system after installation. MVL is automatically installed in the last step of the installation of MCCS.
MVL driver can be installed/unistalled manually through the command of, 'install.bat /uninstall.bat' of the '%MCCS_HOME%\bin\DiskAgent' directory.
MVS is developed in a way of legacy filter driver of Wiindows.
Therefore, service start and stop can be done through net command of Windows.
Following is the way of service start and stop using command line interface.
Start
net start vollock
Stop
net stop vollock
When removing MCCS, removal is done for both MCCS and also MVL. To remove it completely. Execute 'unistall.bat of the bin' %MCCS_HOME%\bin\DiskAgent.
Recommendations for installation and uninstallation
MVL is a legacy kernel filter driver. Thus, you must first run the install.bat / uninstall.bat file provided by MCCS and reboot the system.
Example of Shared Disk Configuration
Following steps are recommended to manage shared disk resource through MVL after installing MCCS.
Assume that a driver letter S: is a shared disk resource in a cluster.Â
- While both nodes (assumed as node A and node B) are in the power off state, bring power online on node A first.
- Install MCCS on node A.
- Add driver S: to MVL though ‘vollock /a s:’ command.
- Lock driver S: through ‘vollock /l s:’ command.
- Check if the driver S: is accessible. The volume access should be denied
- Power online node B when it is checked driver S: is locked to node A
- Apply the same process on node B.
- If both nodes are locked, add a new disk resource.
Maintain the shared disk state to allow one disk access from one node and keep them locked to prevent the damage of data.
MVL Command
Volume control on MVL can be done through Vollock.exe command in '%MCCS_HOME%\bin\DiskAgent'.
vollock [/option] [Drive letter:]
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Option | Description |
L | Locks the disk which is added MVL lock target list. |
U | Unlocks the disk which is added MVL lock target list. |
A | By adding MVL lock target list of Window registry can remain the lock state even after reboot. In addition, it can lock/unlock by adding MVL driver. |
D | Remove the drive letter from MVL lock target list of Window registry. |
W | It shows the state of the specific disk. |
M | It shows whether disk is in mount/unmount state. |
| V | Show MVL version |
status | It shows the state of lock and adding state in table form. |
clear | Unlock all the volumes. |
delete | Delete specific disk. |
'Status' shows the Device Name and Lock information and Registry information as shown below.
[Figure]Â Volume lock Information
Check listÂ
To check if MVL driver is installed, it can be done through checking the list of Vollock driver is listed up by using 'fltmc' command.Â
[Figure] Volume lock Driver Information
vollock.sys is registered through <Legacy> format since it is a legacy kernel filter driver.
Adding
Add the shared disk resource.
Before adding the shared disk resource, be make sure that the driver letter should be located in the external shared storage.
- When add a resource from a group name, select a group → right click → "Add Resource". Or select "Edit(E)" from the main menu bar → select "Add Resource". Or select "Add Resource" icon from the tool bar.
Select "SharedDisk" from Resource Type lists and click the "Next" button. When add a resource from the SharedDisk resource type name, this step will be skipped.
Enter the resource name and select driver letter.
When you select a drive letter, all of driver letters of the node will be displayed. Please note that do not select the driver letter of none shared storage.
[Figure] Adding shared disk resource- As the "Additional Settings" button, you can select check disk option.Â
To use this option, select Use and enter check disk argument. (Default is /F) and click the "OK" button.
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[Figure] Defining check disk option Click the "Finish" button to add the shared disk resource.Â
Deleting
Select "Resource type" → right click → delete resource.
State
The following table explains the state of shared disk resource.Â
Shared disk agent: Manages shared disks registered for MCCS.
| State | Agent command | Description | Note |
|---|---|---|---|
Online The volume is unlocked and is accessible. | Offline | Disables to read or write on a disk by MVL. | |
| Monitoring | Detects whether access for writing to the volume is available or not, by creating MVL and a temporary text file. | ||
Offline The volume is locked and is not accessible to read/write. | Online | Enables to read or write on a disk by MVL. | |
| Monitoring | Detects whether access for writing to the volume is available or not, by creating MVL and a temporary text file. | ||
Fault It indicates that it is unable to write on a volume because external conditions has caused some problem although the volume is online. The problem may occur by the followings: deactivating access to a volume because of external commands or other drivers, or error of physical connection with storages such as FC or SAN switches. | Online | Enables to read or write on a disk by MVL. | |
| Offline | Disables to read or write on a disk by MVL. |
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Attribute
Show the specified attribute of shared disk resource.
| Attribute | Description | Type | Default | Edit | Note |
Chkdsk | If this is set to true, it perform the check disk command when the shared disk is taken online. | BOOLEAN | false | O | |
ChkdskArg | It defines check disk command option when Chkdsk is true. | STRING | /F | O | |
| DirtyBit | It indicates that Dirtybit has been set on a volume for the DirtyBit. Typically, system may apply this setting for inspecting the volume to secure integrity. | BOOLEAN | false | X | |
DriveLetter | It is driver letter of the shared disk. | STRING | O | ||
| forceUmount | If it is set to true, the shared disk will be forcefully unmounted when it is taken offline even tough it has been used. | BOOLEAN | false | O | |
| HostID | Unique server id for scsi reservation | STRING | X | ||
| IOTest | If it's set to true, agent checks if disk is writable. | BOOLEAN | true | O | |
| UseSCSILOCK | If it's set to true, Use SCSI reservation | BOOLEAN | false | O |
Specified attribute values are normally entered when add the resource, This value can be edited or viewed through 'Specified Attribute' table in the Resource Attributes tab on the detailed information panel.
MCCS has function to limit input values against user's input field, and it provides function detects automatically data which is input wrong by user's mistake.
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