Reservation policy from IBM
No Reserve reservationpolicy (不设置任何锁)
If you set MPIO deviceswith this reserve policy, there is no reserve being made on MPIO devices. Adevice without reservation can be accessed by any initiators at any time.Input/output can be sent from all the paths of the MPIO device. This is thedefault reserve policy of SDDPCM.
Exclusive Host Accesssingle-path reservation policy （只允许某一条路径访问，失去了Loadbalance功能）
This is the scsi-2reservation policy. If you set this reserve policy for MPIO devices, only thefail_over path selection algorithm can be selected for the devices. With thisreservation policy, an MPIO device only has one path being opened, and a scsi-2reservation is made by this path on the device. Input/output can only be sentthrough this path. When this path is broken, another path will be opened andscsi-2 reservation will be made by the new path. All input and output will berouted to this path.
Persistent ReserveExclusive Host Access reservation policy（只允许某一个主机访问）
If you set an MPIO devicewith this persistent reserve policy, a persistent reservation is made on thisdevice with a persistent reserve (PR) key. Any initiators who register with thesame PR key can access this device. Normally, you should pick a unique PR keyfor a server. Different servers should have different unique PR key. Input andoutput is routed to all paths of the MPIO device, because all paths of an MPIOdevice are registered with the same PR key. In a nonconcurrent clusteringenvironment, such as HACMP, this is the reserve policy that you should select.
Current HACMP clusteringsoftware supports no_reserve policy with Enhanced Concurrent Mode volume group.HACMP support for persistent reserve policies for supported storage MPIOdevices is not available.
Persistent Reserve SharedHost Access reservation policy
If you set an MPIO devicewith this persistent reserve policy, a persistent reservation is made on thisdevice with a persistent reserve (PR) key. However, any initiators thatimplemented persistent registration can access this MPIO device, even if theinitiators are registered with different PR keys. In a concurrent clusteringenvironment, such as HACMP, this is the reserve policy that you should selectfor sharing resources among multiple servers.
Current HACMP clusteringsoftware supports no_reserve policy with Enhanced Concurrent Mode volume group.HACMP support for persistent reserve policies for supported storage MPIO devicesis not available.