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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) 1 : Type1 controls 'Write" of LUN. When use this option, shared disk resource can be used as lock disk. (Exclusive Write)

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

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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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Image Removed

[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. 

  1. Select a group → right click → 'Add Resource'. 

  2. Select 'SCSILock' from Resource Type lists and click 'Next' button. 

  3. Enter resource name. If you skip enter resource name, this will be given 'SLock_value' which value is selected driver letter.

    [Figure] SCSI Reservation Resource Added

  4. Click the 'Finish' button to add the SCSI reservation resource. 
    You can immediately check the result in the management web console.

Deleting

Select resource type → right click → delete resource.
The deleted resource will immediately disappear from the management web console.

Status

The following table explains the status switching of the MCCS resource caused by a user's command and the status.
The command assumes that it is generated by a user.

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StatusAgent commandDescriptionNote

Online

Disk key is exclusively reserved at an online node.
You cannot register a key at another node. 

Offline

It switches to offline while maintaining the reservation.

 
Monitoring

Check if there is a reservation made on the disk.

 

Offline

1. Disk is reserved but the resource is still offline.
2. The actual offline state where the other node acquired a reservation. 

OnlineRegister a key for a disk reservation and wait for a response from the other node.  
Monitoring

Check if there is a reservation made on the disk.

 

Trouble

It occurs when a reservation is stolen while going online.

OnlineRegister a key for a disk reservation and wait for a response from the other node.  
OfflineIt switches to offline while maintaining the reservation. 

 

 

Attribute

Display the unique attribute of SCSI reservation resource.

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 ) 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.Registor Only) .

INTEGER

Prtype=15O 

 

 

scsicmd.cmd Command

Syntax

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Panel

The output of 'scsicmd' command from source node (C29043F13 is MAC Address of NIC from source node.)

Disk DUID(DeviceUniqueID)LetterPRReserved-KeyRegistered-Keys
0 CNononenone
1 DNononenone
200c0ffd796550000f38be34f01000000EYesnonenone
300c0ffd796550000138ce34f01000000FYesC29043F13*C29043F13*
400c0ffd7965500002e8ce34f01000000GYesnonenone

 

The output of 'scsicmd' command from target node (C29043F13 is MAC Address of NIC from source node.)

Disk DUID(DeviceUniqueID)LetterPRReserved-KeyRegistered-Keys
0 CNononenone
1 DNononenone
200c0ffd796550000f38be34f01000000EYesnonenone
300c0ffd796550000138ce34f01000000FYesC29043F13C29043F13
400c0ffd7965500002e8ce34f01000000GYesnonenone

Disk 0 (C:)'s PR is set to "No". So, you can see that the disk does not support SCSI3-PR.  (In general, the "C" drive is the system booting disk and it does not support SCSI.)
Besides, Disk 1 (D:)'s PR is set to "No". You can see that the disk does not support SCSI3-PR.(Internal Disk does not support SCSI3-PR.)
Disk 2 (E:) and Disk 4 (G:)'s SCSI3-PR is set to "Yes". So, it means that the storage used supports SCSI3- PR. Their Reserved-Key and Registered-Keys are set to "none". It means that they are not yet to be registered.
Disk 3 (F:)'s Reserved-Key and Registered-Keys at the source node are set to C29043F13* and C29043F13* and at the target node to C29043F13 and C29043F13. This means that a SCSI reservation agent was used to create the resource.
The (*) marked node with the Reserved-Key and Registered-Keys indicates that a disk is reserved. In addition, only the * marked node with the Reserved-Key value (ex: C29043F13*) can access the disk.