Displaying detailed information about reclamation commands


Displaying detailed information about reclamation commands
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Dynamic Multi-Pathing (DMP) supports several array-level reclamation commands: UNMAP, WRITE_SAME, TRIM, and PTRIM. The Array Support Library (ASL) for each array uses the most suitable reclamation method from those that are supported for the array. DMP uses the preferred reclamation method that the vendor suggests or selects a reclamation method based on performance analysis.

You cannot change the reclamation method that DMP uses. However, you can view the information about the reclamation command that DMP has selected.

You can view information about other reclamation attributes that DMP uses to create reclamation requests. The reclamation attributes are vendor-specific.

To display information about the thin reclamation methods

To display detailed information about the thin reclamation methods for a device, use the following command:

# vxdisk -p list xiv0_6699

DISK                : xiv0_6699
VID                 : IBM
UDID                : IBM%5F2810XIV%5F0E95%5F1A2B
TP_PREF_RCLMCMD     : write_same
TP_RECLM_CMDS       : write_same, unmap
TP_ALLOC_UNIT       : 1048576
TP_MAX_REC_SIZE     : 268435456
TP_LUN_SHIFT_OF     : 0
SCSI_VERSION        : 5
SCSI3_VPD_ID        : 001738000E951A2B
REVISION            : 10.2
.
.
.
LUN_SIZE            : 33554432
NUM_PATHS           : 4
STATE               : online

The following fields show the information about the reclamation attributes:

TP_PREF_RCLMCMD	The preferred reclaim method for this array.
TP_RECLM_CMDS	The reclamation methods that the underlying device supports.
TP_ALLOC_UNIT	The size in bytes of the allocation unit for thin provisioning on the device.
TP_MAX_REC_SIZE	The maximum size in bytes of the reclamation I/O on the device.
TP_LUN_SHIFT_OF	The value in bytes by which the vendor shifts the initial offset for the LUN. Set this value to align the reclaim request to the TP_ALLOC_UNIT.