The Linux ecosystem provides a variety of open-source filesystem software, making it easy to arrange a filesystem setup that keeps you in control of your data. Volume management is critical to the management of disk space and uses storage virtualization to partition and organize data so you can use it efficiently.
LVM and ZFS are two of the leading options for volume management on Linux, but they have significant differences in scope and performance.
In this article, we share the key differences between LVM and ZFS and which option is best for your volume management needs.
LVM vs. ZFS: Full Comparison
LVM is one of Linux’s leading volume managers and is alongside a filesystem for dynamic resizing of the system disk space. ZFS is a filesystem and volume manager combined. This is a major difference because ZFS organizes and manages your data comprehensively. LVM is not a filesystem but operates in a layer that is distinct from the filesystem to perform disk management.
LVM vs. ZFS: A Side-by-Side Comparison
|What it is||Logical volume manager||Journaling file system and volume manager|
|Primary Use||Disk space management for the Linux kernel||Filesystem for Linux|
|Max Volume Size||165,536 physical extents (PE) per logical volume (LV)||256 trillion yobibytes (2 128 bytes)|
|Max File Size||16 exbibytes (2 64 bytes)||16 exbibytes (2 64 bytes)|
|Max File Name Size||64 characters per logical volume, 126 characters in total (volume group name + logical volume name)||255 ASCII characters|
|Copy on write (CoW)||Yes||Yes|
|Influential Developers||Heinz Mauelshagen, Sistina Software, IBM, Oracle||AT&T, Sun Microsystems, Oracle, OpenZFS|
|Technologies influenced||Linux, Ubuntu, RedHat, Fedora||OpenSolaris, illumos distributions, OpenIndiana, FreeBSD, Mac OS X Server, NetBSD, Linux|
LVM vs. ZFS: 10 Need to Know Facts
- Logical volume managers run alongside a filesystem to provide easy, flexible disk space management.
- LVM is not a filesystem.
- Sun Microsystems originally developed the Zettabyte File System (ZFS) as part of the Solaris OS.
- LVM facilitates the aggregation of multiple separate hard drives or disk partitions into a single volume group (VG). You can then manage the volume groups as single, large volumes, or smaller logical volumes (LVs).
- Both ZFS and LVM use Copy-on-Write (COW), a resource management technique where a copy of original data is held while the source data is modified or updated.
- A logical volume can contain an entire filesystem like ext3 or ext4.
- You can dynamically resize the ext3 and ext4 filesystems, making them ideal for LVM.
- You can expand or reduce the amount of disk space in a logical volume.
- ZFS creates zpools, pooled data from multiple physical disks that it manages as a unified storage pool.
- ZFS organizes and presents its storage pool as a virtual device (vdev).
What is Logical Volume Manager?
Logical Volume Manager, known as LVM, is a volume management tool for the Linux kernel. Linux users run it alongside filesystems to undertake critical tasks like the allocation of disks, mirroring, striping, and resizing of logical volumes.
LVM is advantageous because it is capable of dynamic resizing, so you can allocate more space to a disk while the filesystem is running. LVM has been available since the late 1990s and is compatible with most contemporary Linux distributions.
How Does LVM Work?
LVM takes one or more hard drives and allocates them to physical volumes (PVs), which (except for /boot) are then combined into volume groups (VGs) and individual logical volumes (LVs).
You can create these three elements using the following commands:
- For a physical group use: pvcreate
- For a volume group use: vgcreate
- For a logical volume use: lvcreate
The logical volumes facilitate dynamic volume resizing. LVM can manage hard disk farms with the addition or replacement of disks without system disruption. It can also efficiently resize filesystems at a personal computing level.
LVM also protects data integrity by performing regular snapshots of the logical volumes and ensures security by encrypting multiple physical partitions with a single password. LVM can also include RAID functionality and supports RAID 1, 5, and 6.
The History of LVM
Heinz Mauelshagen, a software engineer at Sistina Software (who is now with RedHat), wrote the original LVM code in 1998. He was the main LVM1 architect/developer, later becoming the team lead device-mapper for LVM2 development. The LVM code was based on the Hewlett-Packard Unix OS volume manager.
LVM has basic and advanced functionality for managing the PVs, VGs, and LVs at scale. Here are some of the notable features:
- You can resize volume groups and logical volumes live online.
- Resize the VGs by adding or ejecting physical volumes.
- Resize the LVs by linking or shortening their constituent extents.
- LVM also allows you to move LVs between PVs.
- LVM uses copy-on-write and can create read-only or read/write snapshots to protect your data.
- You can create LVs with RAID functionality and stripe parts or entire LVs.
- Advanced users of LVM can create hybrid volumes that harness the capacity of flash drives and other fast storage to create caches for the hard disk drive.
- LVM and LVM2 have a device mapper. This framework, which is part of the Linux kernel, maps physical block devices onto virtual block devices.
What is ZFS?
ZFS is a contemporary Linux filesystem that has the added benefit of including a volume manager. It is currently owned by Orcale, Inc., but an open-source version, OpenZFS, is popular with Linux users.
ZFS can pool and manage data from multiple physical storage devices including hard drives and memory cards. It aggregates the data into a zpool that it then organizes for efficient use by the OS. Like any other filesystem, ZFS manages the stored data and files with state-of-the-art data protection to preserve data integrity.
The History of ZFS
Sun Microsystems developed ZFS as the filesystem for its Solaris OS. In 2005, Sun Microsystems made the Solaris OS, including ZFS, open source. A community of developers ported ZFS to Linux where it continued as OpenZFS. In the meantime, Sun Microsystems sold Solaris to Oracle, who continued to develop its own version of ZFS as a commercial product.
Features of ZFS
ZFS is one of the most advanced Linux filesystems. Adding an integrated volume manager makes it even more powerful and adaptive. It is widely used as a filesystem for servers and other enterprise applications.
Its main features include:
- ZFS has one of the largest filesystem capacities available to Linux users. It is almost infinitely scalable while providing a high standard of data integrity and protection. Its 16 exbibytes (264 bytes) file size is the largest available.
- ZFS is unusual because it integrates volume management with a filesystem. This means that it can complete a variety of volume-related tasks that a basic filesystem cannot. It delivers fine management control of your data, including managing tiered storage and caches, data compression, and data deduplication for maximum OS speed and performance.
- ZFS has high read/write efficiency, facilitated by its advanced volume management. It automatically writes to the areas of its filesystem where the most disk space is available.
Despite its large capacity and file sizes, ZFS maintains a high degree of data integrity throughout the filesystem. It uses the following methods to protect data from the effects of corruption or disk failure:
- Snapshots: ZFS uses frequent snapshots of the entire system and will roll back to the most recent snapshot if it finds data corruption.
- Checksumming: Checksums are used to detect errors or corruption with revision to the earlier correct data if necessary.
- RAID-Z: a proprietary form of RAID that delivers targeted and efficient striping of system disks.
LVM vs. ZFS: Which One is Better? Which One Should You Use?
Your choice of LVM or ZFS depends on your filesystem needs.
If you have a filesystem like ext3 or ext4 and need a volume manager, LVM is an ideal add-on as it will work effectively with the filesystem in place.
However, if you are also upgrading your filesystem, ZFS is one of the most advanced Linux filesystems available. The addition of a volume manager means you can be confident that ZFS will manage your data for maximum efficiency.
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