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

Configuration

SCSI-Lock resource can be configured in 2 ways with shared disk resource. Configuration process changes according to the attribute value of SCSI Lock resource.

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1. When shared disk and SCSI Lock resource is configured with the same LUN (PrType=1)When you define an attribute of SCSI Lock resource as PrType=1, you can configure shared disk and SCSI Lock resource with the same LUN.
SCSI Lock LUN 

SCSI Lock agent manages DATA-DISK(shared disk resource) using by MOUNT/UMOUNT command and manages LOCK-DISK(SCSI Lock resource) using by SCSI-3 PR as shown below.
By setting up the dependency between SCSI Lock resources and shared disk resources, any damage of data-disk can be prevented which may occur in such case like Split-Brain.

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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)

At this type, shared disk agent manages DATA-DISK where user data is stored and SCSI lock agent uses exclusive LUN for key reservation. Therefore, two LUNs is required at least.
Lock-disk volume is created for 1:1 dependency with shared disk agent like a figure below.
By using multiple shared disk agents, and one SCSI reservation agent, you can configure the dependency relationship for use.
The storage capacity of this disk can be small 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

DATA-DISK 

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

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 device path that created shared disk resource)
  6. Enable SCSI Lock resource and check key in resource attribute of MCCS web 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

2.Shared disk and SCSI Lock resource configured with different LUN (PrType = 3)

Image Removed

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

Registration Procedures 

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  2. Install MCCS on both nodes
  3. Set group
  4. Add shared disk resource 
  5. Enable shared disk resource and check offline on both nodes
  6. Add SCSI Lock resource (Select new device path which is not assigned for shared disk resource.)
  7. Enable SCSI Lock resource and check Key in resource attribute in MCCS Console
  8. Change PrType 1 to 3 for attribute of SCSI Lock resource
  9. Configure dependency of resources (SCSI Lock resource must go online first)
  10. Test failover from node2 to 1
  11. Test failover from node1 to 2
    12. 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

Data Type

DefaultEditNote
DevicePath

Define the device path of disk to be used for reservation.

When register device path, DUID of connected disk will automatically obtain.

STRING X 
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 
Key

MAC address is used as Reserved-Key. This key is automatically set by agent. 

STRING X 
PreemptWaitCount

Time waiting for permission of other node before reservation

Waiting time is (PreemptWaitCount * MonitorInterval) seconds.

STRING2 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 but MCCS uses 1 5 (Write Exclusive ) or 3 (Exclusive Access).

1 (Write Exclusive) is used when same LUN is used with shared disk.

3 (Exclusive Access) is used when only Lock_Disk is used.

In this case, SCSI Lock agent LUN is required.

Registor Only).

STRING

Prytpe = 15O 

 

 

scsicmd Command

Syntax

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