EX200 Configure local storage Practice Question
A technician is configuring a new Red Hat Enterprise Linux 9 server with multiple disks. They need to create a RAID 1 array using /dev/sda and /dev/sdb for the /boot partition. Which tool can create the RAID array and enable booting from it?
⚠ Common exam trap
Candidates often think LVM mirroring is acceptable for /boot, but Red Hat exams emphasize that /boot must not use LVM or complex RAID levels; only RAID 1 with mdadm and GRUB on both disks is supported for bootability.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use mdadm to create a RAID1 device and install GRUB on both disks
Mdadm is the standard Linux tool for creating software RAID arrays, including RAID 1 (mirroring). For the /boot partition, which must be readable by the bootloader, GRUB must be installed on both disks in the RAID 1 array to ensure bootability if one disk fails. mdadm creates the RAID device, and GRUB can then be installed on each disk's MBR or GPT partition.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use mdadm to create a RAID1 device and install GRUB on both disks
Why this is correct
mdadm is the standard RHEL tool for building software RAID, and RAID1 gives /boot redundancy without requiring GRUB to understand LVM. After creating /dev/md0 from a partition on each disk, run grub2-install on both /dev/sda and /dev/sdb so the BIOS can load GRUB from either disk if one fails. This is the only supported way to get a redundant boot path on a traditional BIOS system.
- ✗
Use parted to create a RAID array directly by specifying the RAID level
Why it's wrong here
parted is a partition editor, not a RAID manager. It can create a partition and set a flag, but it has no concept of RAID levels and cannot assemble a redundant device. The kernel's md driver plus the mdadm utility are what actually create and manage the RAID array. Specifying a RAID level in parted is simply outside its functionality.
- ✗
Use fdisk to create a RAID partition and then format with ext4
Why it's wrong here
fdisk can create a partition and mark its type as 'Linux RAID' (0xFD), but that only flags the partition as available for RAID later. Formatting that underlying partition with ext4 places the filesystem directly on the disk, bypassing the RAID layer entirely, so there is no mirroring. To gain redundancy, you must first use mdadm --create to assemble /dev/md0 from the RAID-typed partitions, then format /dev/md0 with ext4. Formatting a member partition with ext4 would leave the array nonfunctional and data unprotected.
- ✗
Use LVM to create a mirrored logical volume for /boot
Why it's wrong here
LVM can create a mirrored logical volume for /boot, but GRUB does not reliably support reading from LVM mirror segments, particularly in BIOS boot mode. GRUB's core image would need to parse LVM metadata and understand mirror legs, which is fragile and not supported on RHEL 9. The /boot filesystem must be on a plain partition, an mdadm RAID1 device, or a non-mirrored LVM logical volume without RAID redundancy. Thus using an LVM mirror is not a valid or supported way to make /boot redundant.
Quick reference
RAID Level Comparison
| RAID Level | Min Disks | Fault Tolerance | Read | Write | Usable Capacity |
|---|---|---|---|---|---|
| RAID 0 | 2 | None | Excellent | Excellent | 100% |
| RAID 1 | 2 | 1 disk | Good | Moderate | 50% |
| RAID 5 | 3 | 1 disk | Good | Moderate | 67–94% |
| RAID 6 | 4 | 2 disks | Good | Lower | 50–88% |
| RAID 10 | 4 | 1 disk per mirror | Excellent | Good | 50% |
RAID is not a backup strategy — it protects against disk failure but not against accidental deletion, ransomware, or site-level events.
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