Chapter 1. The LVM Logical Volume Manager
Chapter 1. The LVM Logical Volume Manager This chapter provides a summary of the features of the LVM logical volume manager that are new since the initial release of Red Hat Enterprise Linux 7. This chapter also provides a high-level overview of the components of the Logical Volume Manager (LVM). 1.1. New and Changed Features This section lists features of the LVM logical volume manager that are new since the initial release of Red Hat Enterprise Linux 7. 1.1.1. New and Changed Features for Red Hat Enterprise Linux 7.1 Red Hat Enterprise Linux 7.1 includes the following documentation and feature updates and changes. The documentation for thinly-provisioned volumes and thinly-provisioned snapshots has been clarified. Additional information about LVM thin provisioning is now provided in the lvmthin (7) man page. For general information on thinly-provisioned logical volumes, see Section 2.3.4, "Thinly-Provisioned Logical Volumes (Thin Volumes)" . For information on thinly-provisioned snapshot volumes, see Section 2.3.6, "Thinly-Provisioned Snapshot Volumes" . This manual now documents the lvm dumpconfig command in Section B.2, "The lvmconfig Command" . Note that as of the Red Hat Enterprise Linux 7.2 release, this command was renamed lvmconfig , although the old format continues to work. This manual now documents LVM profiles in Section B.3, "LVM Profiles" . This manual now documents the lvm command in Section 3.6, "Displaying LVM Information with the lvm Command" . In the Red Hat Enterprise Linux 7.1 release, you can control activation of thin pool snapshots with the -k and -K options of the lvcreate and lvchange command, as documented in Section 4.4.20, "Controlling Logical Volume Activation" . This manual documents the --force argument of the vgimport command. This allows you to import volume groups that are missing physical volumes and subsequently run the vgreduce --removemissing command. For information on the vgimport command, refer to Section 4.3.15, "Moving a Volume Group to Another System" . This manual documents the --mirrorsonly argument of the vgreduce command. This allows you remove only the logical volumes that are mirror images from a physical volume that has failed. For information on using this option, refer to Section 4.3.15, "Moving a Volume Group to Another System" . In addition, small technical corrections and clarifications have been made throughout the document. 1.1.2. New and Changed Features for Red Hat Enterprise Linux 7.2 Red Hat Enterprise Linux 7.2 includes the following documentation and feature updates and changes. Many LVM processing commands now accept the -S or --select option to define selection criteria for those commands. LVM selection criteria are documented in the new appendix Appendix C, LVM Selection Criteria . This document provides basic procedures for creating cache logical volumes in Section 4.4.8, "Creating LVM Cache Logical Volumes" . The troubleshooting chapter of this document includes a new section, Section 6.7, "Duplicate PV Warnings for Multipathed Devices" . As of the Red Hat Enterprise Linux 7.2 release, the lvm dumpconfig command was renamed lvmconfig , although the old format continues to work. This change is reflected throughout this document. In addition, small technical corrections and clarifications have been made throughout the document. 1.1.3. New and Changed Features for Red Hat Enterprise Linux 7.3 Red Hat Enterprise Linux 7.3 includes the following documentation and feature updates and changes. LVM supports RAID0 segment types. RAID0 spreads logical volume data across multiple data subvolumes in units of stripe size. For information on creating RAID0 volumes, see Section 4.4.3.1, "Creating RAID0 Volumes (Red Hat Enterprise Linux 7.3 and Later)" . You can report information about physical volumes, volume groups, logical volumes, physical volume segments, and logical volume segments all at once with the lvm fullreport command. For information on this command and its capabilities, see the lvm-fullreport (8) man page. LVM supports log reports, which contain a log of operations, messages, and per-object status with complete object identification collected during LVM command execution. For an example of an LVM log report, see Section 4.8.6, "Command Log Reporting (Red Hat Enterprise Linux 7.3 and later)" . For further information about the LVM log report. see the lvmreport (7) man page. You can use the --reportformat option of the LVM display commands to display the output in JSON format. For an example of output displayed in JSON format, see Section 4.8.5, "JSON Format Output (Red Hat Enterprise Linux 7.3 and later)" . You can now configure your system to track thin snapshot and thin logical volumes that have been removed by enabling the record_lvs_history metadata option in the lvm.conf configuration file. This allows you to display a full thin snapshot dependency chain that includes logical volumes that have been removed from the original dependency chain and have become historical logical volumes. For information on historical logical volumes, see Section 4.4.21, "Tracking and Displaying Historical Logical Volumes (Red Hat Enterprise Linux 7.3 and Later)" . In addition, small technical corrections and clarifications have been made throughout the document. 1.1.4. New and Changed Features for Red Hat Enterprise Linux 7.4 Red Hat Enterprise Linux 7.4 includes the following documentation and feature updates and changes. Red Hat Enterprise Linux 7.4 provides support for RAID takeover and RAID reshaping. For a summary of these features, see Section 4.4.3.12, "RAID Takeover (Red Hat Enterprise Linux 7.4 and Later)" and Section 4.4.3.13, "Reshaping a RAID Logical Volume (Red Hat Enterprise Linux 7.4 and Later)" .