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Chapter 16. Storage

Data Deduplication and Compression with VDO

Red Hat Enterprise Linux 7.5 introduces Virtual Data Optimizer (VDO). This feature enables you to create block devices that transparently provide data deduplication, compression, and thin provisioning. Standard file systems and applications can run on these virtual block devices without modification.
VDO is currently available only on the AMD64 and Intel 64 architectures.
For more information on VDO, see the chapter Data Deduplication and Compression with VDO in the Storage Administration Guide: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/vdo. (BZ#1480047)

New boom utility for managing LVM snapshot and image boot entries

This release adds the boom command, which you can use to manage additional boot loader entries on the system. You can use it to create, delete, list, and modify auxiliary boot entries for system snapshots and images. The utility provides a single tool for managing boot menu entries for LVM snapshots; therefore you no longer need to manually edit boot loader configuration files and work with detailed kernel parameters. The tool is provided by the lvm2-python-boom package. (BZ#1278192)

DM Multipath no longer requires reservation keys in advance

DM Multipath now supports two new configuration options in the multipath.conf file:
  • unpriv_sgio
  • prkeys_file
The reservation_key option of the defaults and multipaths sections accepts a new keyword: file. When set, the multipathd service will now use the file configured in the prkeys_file option of the defaults section to get the reservation key to use for the paths of a multipath device. The prkeys file is automatically updated by the mpathpersist utility. The default for the reservation_key option remains undefined, and default for the prkeys_file is /etc/multipath/prkeys.
If the new unpriv_sgio option is set to yes, DM Multipath will now create all new devices and their paths with the unpriv_sgio attribute. This option is used internally by other software, and is unnecessary for most DM Multipath users. It defaults to no.
These changes make it possible to use the mpathpersist utility without knowing ahead of time what reservation keys will be used and without adding them to the multipath.conf configuration file. As a result, it is now easier to use the mpathpersist utility to manage multipath persistent reservations in multiple setups. (BZ#1452210)

New property parameter supported in blacklist and blacklist_exception sections of multipath.conf

The multipath.conf configuration file now supports the property parameter in the blacklist and blacklist_exception sections of the file. This parameter allows users to blacklist certain types of devices. The property parameter takes a regular expression string that is matched against the udev environment variable names for the device.
The property parameter in blacklist_exception works differently than the other blacklist_exception parameters. If the parameter is set, the device must have a udev variable that matches. Otherwise, the device is blacklisted.
Most usefully, this parameter allows users to blacklist SCSI devices that multipath should ignore, such as USB sticks and local hard drives. To allow only SCSI devices that could reasonably be multipathed, set this parameter to (SCSI_IDENT_|ID_WWN) in the blacklist_exceptions section of the multipath.conf file. (BZ#1456955)

smartmontools now support NVMe devices

This update adds support for Nonvolatile Memory Express (NVMe) devices, especially Solid-state Drive (SSD) disks, into the smartmontools package. As a result, the smartmontools utilities can now be used for monitoring NVMe disks with the Self-Monitoring, Analysis and Reporting Technology System (S.M.A.R.T.). (BZ#1369731)

Support for DIF/DIX (T10 PI) on specified hardware

SCSI T10 DIF/DIX is fully supported in Red Hat Enterprise Linux 7.5, provided that the hardware vendor has qualified it and provides full support for the particular HBA and storage array configuration. DIF/DIX is not supported on other configurations, it is not supported for use on the boot device, and it is not supported on virtualized guests.
At the current time, the following vendors are known to provide this support.
FUJITSU supports DIF and DIX on:
EMULEX 16G FC HBA:
  • EMULEX LPe16000/LPe16002, 10.2.254.0 BIOS, 10.4.255.23 FW, with:
  • FUJITSU ETERNUS DX100 S3, DX200 S3, DX500 S3, DX600 S3, DX8100 S3, DX8700 S3, DX8900 S3, DX200F, DX60 S3, AF250, AF650, DX60 S4, DX100 S4, DX200 S4, DX500 S4, DX600 S4, AF250 S2, AF650 S2
QLOGIC 16G FC HBA:
  • QLOGIC QLE2670/QLE2672, 3.28 BIOS, 8.00.00 FW, with:
  • FUJITSU ETERNUS DX100 S3, DX200 S3, DX500 S3, DX600 S3, DX8100 S3, DX8700 S3, DX8900 S3, DX200F, DX60 S3, AF250, AF650, DX60 S4, DX100 S4, DX200 S4, DX500 S4, DX600 S4, AF250 S2, AF650 S2
Note that T10 DIX requires database or some other software that provides generation and verification of checksums on disk blocks. No currently supported Linux file systems have this capability.
EMC supports DIF on:
EMULEX 8G FC HBA:
  • LPe12000-E and LPe12002-E with firmware 2.01a10 or later, with:
  • EMC VMAX3 Series with Enginuity 5977; EMC Symmetrix VMAX Series with Enginuity 5876.82.57 and later
EMULEX 16G FC HBA:
  • LPe16000B-E and LPe16002B-E with firmware 10.0.803.25 or later, with:
  • EMC VMAX3 Series with Enginuity 5977; EMC Symmetrix VMAX Series with Enginuity 5876.82.57 and later
QLOGIC 16G FC HBA:
  • QLE2670-E-SP and QLE2672-E-SP, with:
  • EMC VMAX3 Series with Enginuity 5977; EMC Symmetrix VMAX Series with Enginuity 5876.82.57 and later
Please refer to the hardware vendor's support information for the latest status.
Support for DIF/DIX remains in Technology Preview for other HBAs and storage arrays. (BZ#1499059)

File system Direct Access (DAX) and device DAX now support huge pages

Previously, each file system DAX and device DAX page fault mapped to a single page in the user space. With this update, file system DAX and device DAX can now map persistent memory in larger chunks, called huge pages.
File system DAX supports huge pages that are, for example, 2 MiB in size on the AMD64 and Intel 64 architectures, and device DAX supports using either 2 MiB or 1 GiB huge pages on AMD64 and Intel 64. In comparison, a standard page is 4 KiB in size on the these architectures.
When creating a DAX namespace, you can configure the page size that the namespace should use for all page faults.
Huge pages lead to fewer page faults, smaller page tables, and less Translation Lookaside Buffer (TLB) contention. As a result, file system DAX and device DAX now use less memory and perform better. (BZ#1457561, BZ#1383493)

fsadm can now grow and shrink LUKS-encrypted LVM volumes

The fsadm utility is now able to grow and shrink Logical Volume Manager (LVM) volumes that are encrypted with Linux Unified Key Setup (LUKS). This applies both to using fsadm directly with the fsadm --lvresize command and to using it indirectly through the lvresize --resizefs command.
Note that due to technical limitations, resizing of encrypted devices with a detached header is not supported. (BZ#1113681)