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External storage must support SCSI-3 PR.
Volume should be configured by LUN(Logical Unit Number) unit. Partitioned volume in a LUN is not supported.If use PrType 3, at least 1GByte LUN is needed for key reservation.

 

 

Types of Shared disk resource

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2. Both the shared disk agent and the SCSI reservation agent can read and write data.
However, a SCSI reservation agent intends to protect the shared storage resource, so you are not recommended to use it alone to read and write data.
Thus, a SCSI reservation agent can be used together with a shared storage agent or can use a separate LUN from the shared storage (PrType option)

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PrType (Persist Type) 3 : Typ3 controls "Access" of LUN. When use this option, exclusive LUN is needed for lock disk

Small disk capacity of about 1GB is available. But the content is not protected.

 

 

Configuration

 

There are two different ways to configure the SCSI reservation agent resource and the shared disk agents resource. It depends on the attribute of the SCSI reservation agent resource.

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1. When shared disk and SCSI Lock resource is configured with the same LUN (PrType=1)

In the SCSI reservation agent resource, use the option of PrType = 1. In this case, LUN will be used to configure the shared disk resource and the SCSI reservation resource.
A shared disk agent uses the MVL driver to manage DATA-DISK and a SCSI reservation agent uses the SCSI3-PR function to manage LOCK-DISK.
By setting the dependency between the SCSI reservation resource and the shared disk resource, you can prevent damages to DATA-DISK caused by Split-Brains and so on.

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[Figure] Shared disk and SCSI Lock resource configured in same LUN (PrType=1)2. Shared disk and SCSI lock resource is configured with different LUN (PrType=3)A shared disk agent manages DATA-DISK on the single drive character basis, and a SCSI reservation agent manages the standalone LUN exclusively for LOCK-DISK.
For this configuration, there must be at least two LUN segments existing on the shared disk.
As shown below, create the LOCK-DISK volume that will depend on a shared disk agent in a 1:1 relationship.
By using multiple shared disk agents, and one SCSI reservation agent, you can configure the dependency for use.
This disk with small capacity is allowed because it is used to check the node that can access the storage.
By setting the dependency between the SCSI reservation resource and the shared disk resource, you can prevent damages to DATA-DISK caused by Split-Brains and so on.


Image Removed   [Figure] Shared disk and SCSI Lock resource is configured with different LUN( PrType=3)

Info

Meaning of DATA-DISK

  • It is a disk created by using a shared disk agent. It represents a disk where the actual user data is used.  

Meaning of LOCK-DISK

  • It is a disk created by using a SCSI reservation agent.
    This is the disk that depends on DATA_DISK used in the shared disk when linking a shared disk agent.

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1. Shared disk and SCSI Lock resource is configured in same LUN (PrType=1).

[Figure] Shared disk and SCSI Lock resource configured in same LUN

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  1. Install MCCS on both nodes
  2. Set group
  3. Add shared disk resource
  4. Enable shared disk resource and check offline on both nodes
  5. Add SCSI Lock resource (Select drive letter that created shared disk resource)
  6. Enable SCSI Lock resource and check key in resource attribute of MCCS console.
  7. Configure dependency of resources (SCSI Lock resource must go online first)
  8. Test failover from node 2 to 1 
  9. Test failover from node 1 to 2
  10. Set application that customer uses

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[Figure] Shared disk and SCSI Lock resource configured with different LUN 

First, register shared disk agent according to the procedure and after check if it works normally, check disk of SCSI Lock agent.  

  1. Install MCCS on both nodes
  2. Set group
  3. Add shared disk resource 
  4. Enable shared disk resource and check offline on both nodes
  5. Add SCSI Lock resource (Select new drive letter, not from the one in shared disk resource)
  6. Enable SCSI Lock resource and check Key in resource attribute in MCCS Console
  7. Change PrType 1 to 3 for attribute of SCSI Lock resource. (When SCSI Lock resource is added, make sure that SCSI Lock Disk Letter are disappeared from Windows Explorer of both servers.)
  8. Configure dependency of resources (SCSI Lock resource must go online first)
  9. Test failover from node2 to 1
  10. Test failover from node1 to 2
  11. Customer applications that use the volume setting

 

 



Adding

Add the SCSI reservation application resource to a group.
Before configuring the SCSI reservation resource, you must configure the volume in advance by using the SCSI3 supporting storage. 

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Attribute

Description

Type

DefaultEditNote
DiskDUID

DUID(Device Unique ID, 16 byte as Hex value) of disk is used as identifier. Specify DUID of reserve disk.
This value is secure when DriveLetter atribute us specified. Try not to insert this value yourself.
DUID information can be checked through scsicmd.cmd command and both nodes need to have the same value.

STRING X 
DriveLetter

Disk to be used for reservation is specified by drive letter.
When register drive letter, DUID of connected disk will automatically obtain in drive letter.

STRING X 
KeyMAC address is used as Reserved-Key. This key is automatically set by agent.STRING   
PreemptWaitCount

Time waiting for permission of other node before reservation
Waiting time is (PreemptWaitCount * MonitorInterval) seconds.

INTEGER2 timesO 
PrType

This attribute decides on how to give the permission of reserve disk access as Persist Type specified in SCSI3-PR spec.
There are 6 types bur MCCS uses 1 5 (Write Exclusive Registor Only) or 3 (Exclusive Access).
1 (Write Exclusive) is used when same LUN is used with shared disk, and Disk Letter can be checked in explorer.
3 (Exclusive Access) is used when only Lock_Disk is used.
In this case, SCSI Lock agent LUN is required. 'Mount' state of disk changes to 'un-mount' state.Therefore, Disk Letter will disappear from explorer.

INTEGER

Prtype=15O 

 

 

scsicmd.cmd Command

Syntax

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