SG_REM_REST_ELEM(8) SG3_UTILS SG_REM_REST_ELEM(8)

sg_rem_rest_elem - send SCSI remove or restore element command

sg_rem_rest_elem [--capacity=RC] [--element=EID] [--help] [--quick] [--remove] [--restore] [--timeout=SE] [--verbose] [--version] DEVICE

Sends a SCSI REMOVE ELEMENT AND TRUNCATE [RMEAT] or RESTORE ELEMENTS AND REBUILD [RSEAR] command to the DEVICE. Since both these commands have a potentially huge impact on the DEVICE (similar to the FORMAT UNIT command: destroying data and taking a long time to complete fully), they first give the user the chance to reconsider (3 times within 15 seconds) before taking action.

Unlike the FORMAT UNIT command, these commands seem designed to work in the background. So they will return quickly (although sbc5r01.pdf does not state that) and the disk will be placed in a reduced functionality state where only a specified number of commands will be executed (e.g. INQUIRY and REPORT LUNS) until the operation is complete. Other commands will receive sense data with a sense key of NOT READY and an additional sense code of 'Depopulation in progress' (for RMEAT) or 'Depopulation restoration in progress' (for RSEAR).

The REMOVE ELEMENT AND TRUNCATE has a close relative in ZBC-2 called the REMOVE ELEMENT AND MODIFY ZONES [RMEMZ] command. See the sg_zone utility for an implementation of the latter command.
The difference between RMEAT and RMEMZ is that the former "changes the association between LBAs and physical blocks" and the latter does not change that association. Zones affected by the RMEMZ command are placed into the zone condition: "Offline".

Arguments to long options are mandatory for short options as well.

RC stands for Requested Capacity and is the number of logical blocks the DEVICE should have after the element is removed with the RMEAT command. The default value is 0 which allows the DEVICE to decide what the reduced capacity will be after the element removal. The RSEAR command ignores this value.
where EID is an element identifier which is a 32 bit unsigned integer starting at one. This field is used by the RMEAT command and ignored otherwise. The default value is zero (which is invalid). So the user needs to supply a valid element identifier when --remove is used.
output the usage message then exit.
the default action (i.e. when this option is not given) is to give the user 15 seconds to reconsider doing a remove or restore element operation on the DEVICE. When this option is given that step (i.e. the 15 second warning period) is bypassed.
causes the REMOVE ELEMENT AND TRUNCATE command to be sent to the DEVICE. In practice, --element=EID needs to be also given.
causes the RESTORE ELEMENTS AND REBUILD command to be sent to the DEVICE.
where SE is the command timeout in seconds. The default is 60 seconds and if 0 is given, it is mapped to 60. An alternate long form is --tmo=SE.
increase the level of verbosity, (i.e. debug output).
print the version string and then exit.

Once an element is removed successfully it is termed as "depopulated". Depopulated elements that have the 'Restoration Allowed' (RALWD) bit set (see sg_get_elem_status) are candidates for future restoration.

A (storage) element of a rotating hard disk is one side of a platter typically associated with one head. Such hard disks typically have multiple platters with two heads per platter (i.e. one head each side of the platter).

The exit status of sg_rem_rest_elem is 0 when it is successful. Otherwise see the sg3_utils(8) man page.

Written by Douglas Gilbert.

Report bugs to <dgilbert at interlog dot com>.

Copyright © 2022-2023 Douglas Gilbert
This software is distributed under a BSD-2-Clause license. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

sg_get_elem_status,sg_zone(sg3_utils)

May 2023 sg3_utils-1.48