How to change between the Write-through Cache and Write-Back Cache on Storage?

Solution In Progress - Updated -

Issue

  • How to change/switch between the Write-through Cache and Write-Back Cache on the storage end?
  • When discovering the LUN, the linux kernel enables "write-through" for the AMS1000 and "write-back" for the AMS2300.
  • The "write-through" gives poor performances in this situation. How can I force linux to enable the "write back" feature ?
Feb 14 11:29:56 kernel:   Vendor: HITACHI   Model: DF600F            Rev: 0000
Feb 14 11:29:56 kernel:   Type:   Direct-Access                      ANSI SCSI revision: 03
Feb 14 11:29:56 kernel: SCSI device sda: 122159104 512-byte hdwr sectors (62545 MB)
Feb 14 11:29:56 kernel: sda: Write Protect is off
Feb 14 11:29:56 kernel: SCSI device sda: drive cache: write through
Feb 14 11:29:56 kernel: SCSI device sda: 122159104 512-byte hdwr sectors (62545 MB)
Feb 14 11:29:56 kernel: sda: Write Protect is off
Feb 14 11:29:56 kernel: SCSI device sda: drive cache: write through ( ====> AMS 1000 <=======)
Feb 14 11:29:56 kernel:  sda: sda1
Feb 14 11:29:56 kernel: sd 0:0:0:0: Attached scsi disk sda
Feb 14 11:29:56 kernel:   Vendor: HITACHI   Model: DF600F            Rev: 0000
Feb 14 11:29:56 kernel:   Type:   Direct-Access                      ANSI SCSI revision: 04
Feb 14 11:29:56 kernel: SCSI device sdb: 2097152 512-byte hdwr sectors (1074 MB)
Feb 14 11:29:56 kernel: sdb: Write Protect is off
Feb 14 11:29:56 kernel: SCSI device sdb: drive cache: write back
Feb 14 11:29:56 kernel: SCSI device sdb: 2097152 512-byte hdwr sectors (1074 MB)
Feb 14 11:29:56 kernel: sdb: Write Protect is off
Feb 14 11:29:56 kernel: SCSI device sdb: drive cache: write back (=======> AMS 2300 <============)
Feb 14 11:29:56 kernel:  sdb: sdb1
Feb 14 11:29:56 kernel: sd 0:0:1:1: Attached scsi disk sdb
Feb 14 11:29:56 kernel:   Vendor: HITACHI   Model: DF600F            Rev: 0000
Feb 14 11:29:56 kernel:   Type:   Direct-Access                      ANSI SCSI revision: 04
Feb 14 11:29:56 kernel:   Vendor: HITACHI   Model: DF600F            Rev: 0000
Feb 14 11:29:56 kernel:   Type:   Direct-Access                      ANSI SCSI revision: 03
Feb 14 11:29:56 kernel: SCSI device sdc: 2097152 512-byte hdwr sectors (1074 MB)
Feb 14 11:29:56 kernel: sdc: Write Protect is off

Environment

  • Red Hat Enterprise Linux (RHEL) all versions

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