Post stating point-wise differences between LVM and LVM2 explained. This is one of the frequently asked questions for the Linux interview.
One of the frequently asked Linux interview questions is ‘what is the difference between LVM and LVM2?’ to which most of the candidate’s flanks. In this article, we will be discussing this question.
First of all, what is LVM? LVM is a logical volume manager. It is a widely used volume manager in Linux and Unix like VxVM (Veritas volume manager). As a sysadmin, you must be knowing all tasks which can be done in LVM but not a theoretical question like the difference between LVM and LVM2.
LVM and LVM2 are two different versions of LVM. Obviously, LVM2 being the latest. Their differences can be identified in terms of their functions, services offered, availability, etc. Let’s see one by one :
LVM is available in most of the famous distributions like HPUX, Redhat, Suse, etc. LVM2 is available only kernel version 2.6.9 and above like RHEL4 and later. You can even build LVM modules as per your kernel (if its not available in your distributions). Setup information can be found here.
LVM2 has backward compatibility with LVM. It has the same command modules and infrastructure like LVM with enhanced features. LVM being the previous version don’t have compatibility with LVM2 features.
Size limits :
Different size limits are increased in the new LVM2. The maximum file system/device size was capped to 2TB in LVM whereas its 16TB(32-bit CPU) & 8EB (64 bit CPU) in LVM2.
Max LV and PV were 255 in LVM. In LVM2 it has no limit (snippet from vgcreate manpage below).
-l, --maxlogicalvolumes MaxLogicalVolumes Sets the maximum number of logical volumes allowed in this vol- ume group. The setting can be changed with vgchange. For vol- ume groups with metadata in lvm1 format, the limit and default value is 255. If the metadata uses lvm2 format, the default value is 0 which removes this restriction: there is then no limit. -p, --maxphysicalvolumes MaxPhysicalVolumes Sets the maximum number of physical volumes that can belong to this volume group. The setting can be changed with vgchange. For volume groups with metadata in lvm1 format, the limit and default value is 255. If the metadata uses lvm2 format, the value 0 removes this restriction: there is then no limit.
Extra features :
LVM2 is bundled with below extra features over LVM :
- Volume mirroring support
- Shared volume support with GFS
- Transnational metadata for fast recovery
- Cluster suite failover supported
- Striped volume expansion
This sums up the difference between LVM and LVM2 versions. Write to us in comments if you have corrections/suggestions.