Using LVM Cache
LVM (Logical Volume Manager) is a feature available on almost all Linux distributions, allowing you to manage your storage media more flexibly and efficiently. LVM Cache is an additional feature available on LVM version 2.02.105 or later, which allows you to use the SSD as a cache for HDDs. This feature can improve your computer’s performance and speed by using intelligent algorithms to learn your usage patterns and store the most frequently accessed data on the SSD.
To use LVM Cache, you need an SSD with a minimum capacity of 8 GB and an HDD with a capacity of at least 100 GB. You also need a Linux operating system with LVM version 2.02.105 or later, with BIOS mode set to AHCI or RAID. The following are the steps to use LVM Cache:
- Plug your SSD and HDD into your computer, and make sure they are detected by Linux.
- Install the lvm2 package that corresponds to your Linux distribution. You can use commands like sudo apt install lvm2 for Ubuntu, or sudo yum install lvm2 for Fedora.
- Create LVM type partitions on your SSD and HDD by using commands such as sudo fdisk /dev/sdX and sudo fdisk /dev/sdY, where /dev/sdX is the name of your SSD, and /dev/sdY is the name of your HDD. You can use the sudo fdisk -l command to see the names of the partitions you created, for example /dev/sdX1 and /dev/sdY1.
- Create a physical volume (PV) on the partition you created by using commands such as sudo pvcreate /dev/sdX1 and sudo pvcreate /dev/sdY1, where /dev/sdX1 is your SSD partition, and /dev/sdY1 is your HDD partition.
- Create a volume group (VG) by using a command such as sudo vgcreate vgcache /dev/sdX1 /dev/sdY1, where vgcache is the name of the VG you want, and /dev/sdX1 and /dev/sdY1 are the PVs you created earlier.
- Create a logical volume (LV) for the data on your HDD by using a command like sudo lvcreate -l 100%FREE -n lvdata vgcache /dev/sdY1, where lvdata is the name of the LV you want, and /dev/sdY1 is the PV of your HDD. You can use the sudo vgs and sudo lvs commands to view the status of your VG and LV.
- Create an LV to cache on your SSD by using a command like sudo lvcreate -L 8G -n lvcache vgcache /dev/sdX1, where lvcache is the name of the LV you want, and /dev/sdX1 is your SSD PV. You can adjust the cache size according to your needs, but make sure it doesn’t exceed the capacity of your SSD.
- Create an LV for the cache pool on your SSD by using a command like sudo lvconvert –type cache-pool –poolmetadata vgcache/lvcache vgcache/lvdata, where vgcache/lvcache is the cache LV you created earlier, and vgcache/lvdata is the data LV you created earlier. This command will convert the cache LV into a cache pool, which will be used to store cached data from the data LV.
- Create an LV for the logical volume (CLV) cache by using a command such as sudo lvconvert –type cache –cachepool vgcache/lvcache vgcache/lvdata, where vgcache/lvcache is the LV cache pool you created earlier, and vgcache/lvdata is the data LV you created earlier. This command will convert the LV data into CLV, which will use the LV cache pool as a cache for the data stored on the HDD.
- Create a filesystem on your CLV by using a command like sudo mkfs.ext4 /dev/vgcache/lvdata, where /dev/vgcache/lvdata is the name of your CLV. You can use the sudo blkid command to view the UUID of your CLV, which you will use to install your CLV.
- Insert the following lines into the /etc/fstab file to automatically install your CLV at boot:
UUID=UUID_CLV /min/cache ext4 defaults 0 2
where UUID_CLV is the CLV UUID you see with the sudo blkid command, and /mnt/cache is the location you want to install your CLV. 12. Run the command sudo mount -a to install your CLV, or restart your computer. Now, your SSD has served as a cache for your HDD, and you can enjoy better performance and speed.