LFCS Storage Management — 10 Questions

Question 1

Which TWO commands can be used to create a new physical volume for use with LVM? (Choose two.)

Accepted Answer

pvcreate /dev/sdb1. To create a physical volume for LVM, the correct command is `pvcreate /dev/sdb1`, which initializes the device as a PV by writing LVM metadata. Option D (`fdisk /dev/sdb` with type 8e) only creates a partition and sets its type to Linux LVM; it does not initialize the partition as a PV. A subsequent `pvcreate` is required to actually create the PV.

Answer

mkfs.ext4 /dev/sdb1

Answer

pvresize /dev/sdb1

Answer

fdisk /dev/sdb (then set type to 8e)

Answer

pvdisplay /dev/sdb1

Question 2

A system administrator is tasked with setting up a new 2TB disk for a database server. The database requires high read/write performance and redundancy. The server has a hardware RAID controller, but the administrator wants to use Linux software RAID for flexibility. Which of the following RAID levels should the administrator choose to maximize performance while providing fault tolerance, assuming the disk will be part of a larger array in the future?

Accepted Answer

RAID 10. RAID 10 (striping of mirrors) provides both high read/write performance and fault tolerance by combining the speed of RAID 0 striping with the redundancy of RAID 1 mirroring. Since the administrator plans to add more disks to the array in the future, RAID 10 scales well with additional pairs, maintaining performance and redundancy without the parity calculation overhead of RAID 5 or RAID 6.

Answer

RAID 5

Answer

RAID 0

Answer

RAID 6

Question 3

An administrator wants to extend a logical volume named 'lv_data' in volume group 'vg_data' by 5GB. The volume group has free physical extents. Which command should be used?

Accepted Answer

lvextend -L +5G /dev/vg_data/lv_data. The correct command to extend a logical volume is `lvextend`. Option B uses the correct syntax with the `-L +5G` flag, which adds 5GB to the existing logical volume `/dev/vg_data/lv_data`. The volume group `vg_data` has free physical extents, so the extension can proceed without needing to add new physical volumes.

Answer

pvextend -L +5G /dev/vg_data/lv_data

Answer

lvresize -L +5G /dev/vg_data/lv_data

Answer

lvextend -L 5G /dev/vg_data/lv_data

Question 4

A storage administrator notices that a newly created XFS filesystem on a logical volume shows only 90% of the expected capacity. The logical volume is 100GB. What is the most likely cause?

Accepted Answer

The filesystem was created with a reduced size due to mkfs.xfs default settings.. B is correct because `mkfs.xfs` by default reserves 10% of the filesystem space for metadata and performance optimization (the `-i maxpct` and internal log overhead). This is not a capacity loss but a design feature of XFS, which explains why a 100GB logical volume shows only ~90GB usable.

Answer

The disk has bad blocks that were marked as unusable.

Answer

The volume group has insufficient physical extents.

Answer

The filesystem is mounted with the 'noatime' option.

Question 5

Which command can be used to display the UUID of a filesystem on /dev/sdb1?

Accepted Answer

blkid /dev/sdb1. The blkid command is specifically designed to locate and print block device attributes, including the UUID and filesystem type. When run against a device like /dev/sdb1, it queries the kernel's device mapper and reads the filesystem superblock to extract the universally unique identifier (UUID). This is the most direct and reliable method for displaying a filesystem's UUID.

Answer

tune2fs -l /dev/sdb1

Answer

df -h /dev/sdb1

Answer

lsblk /dev/sdb1

Question 6

An administrator needs to mount an XFS filesystem with options to optimize for a database workload. Which mount option would reduce metadata updates to improve performance?

Accepted Answer

noatime. The `noatime` mount option disables updates to the inode access time (atime) on every file read. For database workloads, this eliminates a significant source of metadata write I/O, reducing disk contention and improving overall performance by avoiding unnecessary journal updates on XFS.

Answer

noexec

Answer

nodiratime

Answer

relatime

Question 7

Which THREE are valid reasons to use a swap file instead of a swap partition? (Choose three.)

Accepted Answer

Can be placed on a filesystem that supports sparse files.. Swap files can be placed on filesystems that support sparse files (e.g., ext4, XFS). A sparse file allocates disk blocks only when data is written, allowing a large swap file to be created without consuming the full physical disk space immediately. This is useful for systems where disk space is at a premium or where swap size needs to be overcommitted.

Answer

Required for hibernation (suspend-to-disk).

Answer

Faster performance than swap partition.

Question 8

You are a Linux administrator at a mid-sized company. The company runs a critical PostgreSQL database on a server running CentOS 7. The database stores its data on a 500GB logical volume (lv_pgdata) in volume group vg_pg. The filesystem is XFS. Recently, the database team reports that write performance is degrading, and the disk is nearly full (95% usage). You have added a new 200GB SSD to the server, and you need to increase the storage capacity and improve write performance for the database. The database can tolerate a brief downtime (less than 5 minutes) for maintenance. You want to use LVM to add the new SSD as a physical volume, extend the volume group, and then extend the logical volume and filesystem. Additionally, you want to improve write performance by placing the frequently written database transaction log on a separate faster storage. However, the database configuration expects the transaction log to be in a subdirectory of the data directory. You have the following options: A. Create a new logical volume for the transaction log, format it as XFS, mount it on the data directory's subdirectory, and move the log files. B. Add the SSD as a PV, extend vg_pg, extend lv_pgdata, and then use LVM's pvmove to move all extents to the SSD. C. Add the SSD as a PV, create a new VG, create a new LV for the transaction log, format as ext4, mount, and reconfigure the database. D. Use LVM's striping (RAID 0) across the existing HDD and new SSD to improve performance, then extend the filesystem. Which option best meets the requirements of increasing capacity and improving write performance with minimal downtime?

Accepted Answer

Add the SSD as a PV, extend vg_pg, extend lv_pgdata and resize the filesystem for capacity. Then create a new LV on the SSD, format as XFS, mount it on the transaction log subdirectory, move the log files, and update the database configuration to point to the new location.. It directly addresses both requirements: increasing capacity by extending the existing logical volume and filesystem using the new SSD as a PV, and improving write performance by isolating the database transaction log onto the faster SSD via a separate LV mounted on the expected subdirectory. This approach minimizes downtime (under 5 minutes) by performing the resize and mount operations quickly, and it respects the database's configuration expectation that the transaction log resides in a subdirectory of the data directory.

Answer

Add the SSD as a PV, extend vg_pg, extend lv_pgdata and resize the filesystem for capacity. Then use pvmove to move all data to the SSD, leaving the HDD unused.

Answer

Use LVM's striping (RAID 0) across the existing HDD and new SSD to improve performance, then extend the filesystem.

Answer

Add the SSD as a PV, create a new VG and LV for the transaction log, format as ext4, mount, and reconfigure the database to use the new location.

Question 9

A system administrator notices that a new 500GB SSD (/dev/sdb) is not being recognized by the system after installation. The server uses UEFI and GPT partitioning. Which command should the administrator run first to verify that the disk is detected by the kernel?

Accepted Answer

lsblk. The `lsblk` command lists all block devices recognized by the kernel, including those without a filesystem or partition table. Since the disk is new and not yet partitioned, `lsblk` will show it if the kernel has detected it, making it the correct first diagnostic step.

Answer

fdisk -l /dev/sdb

Answer

cat /proc/cpuinfo

Answer

lsusb

Question 10

A Linux administrator needs to create a RAID 5 array using three disks: /dev/sdb, /dev/sdc, and /dev/sdd, each 2TB. The administrator wants to ensure the array can be reassembled automatically after a reboot. Which command should be used to create the array?

Accepted Answer

mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=1.2. It uses `--metadata=1.2`, which stores the superblock at a standard 4 KiB offset from the start of each device, enabling the kernel to automatically discover and assemble the RAID array on reboot without manual intervention. RAID 5 with three disks provides striping with distributed parity, offering a balance of performance and redundancy.

Answer

mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=0.90

Answer

mdadm --create /dev/md0 --level=1 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd

Answer

mdadm --create /dev/md0 --level=0 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd