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5.6. RAID and Other Disk Devices

Some storage technology requires special consideration when using Red Hat Enterprise Linux. Generally, it is important to understand how these technologies are configured, visible to Red Hat Enterprise Linux, and how support for them might have changed between major versions.

5.6.1. Hardware RAID

RAID (Redundant Array of Independent Disks) allows a group, or array, of drives to act as a single device. Configure any RAID functions provided by the mainboard of your computer, or attached controller cards, before you begin the installation process. Each active RAID array appears as one drive within Red Hat Enterprise Linux.

5.6.2. Software RAID

On systems with more than one hard drive, you can use the Red Hat Enterprise Linux installation program to operate several of the drives as a Linux software RAID array. With a software RAID array, RAID functions are controlled by the operating system rather than dedicated hardware. These functions are explained in detail in Section 8.14.4, “Manual Partitioning”.

Note

When a pre-existing RAID array's member devices are all unpartitioned disks/drives, the installer will treat the array itself as a disk and will not provide a way to remove the array.

5.6.3. USB Disks

You can connect and configure external USB storage after installation. Most such devices are recognized by the kernel and available for use at that time.
Some USB drives might not be recognized by the installation program. If configuration of these disks at installation time is not vital, disconnect them to avoid potential problems.

5.6.4. NVDIMM devices

To use a Non-Volatile Dual In-line Memory Module (NVDIMM) device as storage, the following conditions must be satisfied:
  • Version of Red Hat Enterprise Linux is 7.6 or later.
  • The architecture of the system is Intel 64 or AMD64.
  • The device is configured to sector mode. Anaconda can reconfigure NVDIMM devices to this mode.
  • The device must be supported by the nd_pmem driver.
Booting from a NVDIMM device is possible under the following additional conditions:
  • The system uses UEFI.
  • The device must be supported by firmware available on the system, or by a UEFI driver. The UEFI driver may be loaded from an option ROM of the device itself.
  • The device must be made available under a namespace.
To take advantage of the high performance of NVDIMM devices during booting, place the /boot and /boot/efi directories on the device. See Section 8.14.4, “Manual Partitioning” for more information. Note that the Execute-in-place (XIP) feature of NVDIMM devices is not supported during booting and the kernel is loaded into conventional memory.

5.6.5. Considerations for Intel BIOS RAID Sets

Red Hat Enterprise Linux 7 uses mdraid for installation onto Intel BIOS RAID sets. These sets are detected automatically during the boot process and their device node paths can change from boot to boot. For this reason, local modifications to /etc/fstab, /etc/crypttab or other configuration files which refer to devices by their device node paths might not work in Red Hat Enterprise Linux 7. Therefore, you should replace device node paths (such as /dev/sda) with file system labels or device UUIDs instead. You can find the file system labels and device UUIDs using the blkid command.

5.6.6. Considerations for Intel BIOS iSCSI Remote Boot

If you are installing using Intel iSCSI Remote Boot, all attached iSCSI storage devices must be disabled, otherwise the installation will succeed but the installed system will not boot.