Frequently Asked Questions

Welcome to the Lustre FAQ!

What is Lustre?
Lustre is a scale-out architecture distributed parallel filesystem. Metadata services and storage are segregated from data services and storage.

What is the difference between a server (MDS/OSS) and a target (MDT/OST)?
A target is the storage device where object (file) or metadata is kept. The servers service request from clients on their behalf. Clients do not access storage directly.

Why does lists.lustre.org say "The list overview page has been disabled temporarily"?
The mailing lists at lists.lustre.org are running on a fully vendor managed solution at DreamHost. Unfortunately, they have disabled the list overview page for all of their customers, and they have no definitive plan to correct that in the near future. "Temporarily" apparently really means "permanently". While this is unfortunate, DreamHost's mailing list servers are pleasantly fast, low in maintenance, and low in cost. We will just need to live with this minor inconvenience. In the mean time, you can get a full list of mailing lists from Mailing Lists and IRC.

What do all these acronyms mean?

 * DNE - Distributed Namespace Environment - feature aggregating multiple MDTs (possibly on multiple MDSes) into a single filesystem namespace
 * IDIF - OST object ID In FID - specific FID range reserved for compatibility with pre-DNE OST objects
 * IGIF - Inode and Generation In FID - specific FID range reserved for compatibility from Lustre 1.x MDT inode objects
 * FID - File IDentifier - unique 128-bit identifier for every object within a single filesystem, made up of a 64-bit sequence, a 32-bit object ID, and a 32-bit version field
 * IOV - I/O Vector
 * LMV - Logical Metadata Volume - client software layer that handles client (llite) access to multiple MDTs
 * LNET - Lustre Network - Type agnostic networking layer (TCP/IP on Ethernet, InfiniBand, Omni-Path, Cray Gemini, etc.)
 * LOD - Logical Object Device - MDS software layer that handles access to multiple MDTs and multiple OSTs
 * LOV - Logical Object Volume - client software layer that handles client (llite) access to multiple OSTs
 * MDC - MetaData Client - client software layer that interfaces to the MDS
 * MDD - Metadata Device Driver - MDS software layer that understands POSIX semantics for file access
 * MDS - MetaData Server - software service that manages access to filesystem namespace (inodes, paths, permission) requests from the client.
 * MDT - MetaData Target - storage device that holds the filesystem metadata (attributes, inodes, directories, xattrs, etc)
 * MGS - ManaGement Server - service that helps clients and servers with configuration
 * MGT - ManaGement Target - storage device that holds the configuration logs
 * NID - Network Identifier - used to uniquely identify a Lustre network endpoint by node ID and network type.
 * OFD - Object Filter Device - OSS software layer that handles file IO
 * OSC - Object Storage Client - client software layer that interfaces to the OST
 * OSD - Object Storage Device - server software layer that abstracts MDD and OFD access to underlying disk filesystems like ldiskfs and ZFS
 * OSP - Object Storage Proxy - server software layer that interfaces from one MDS to the OSD on another MDS or another OSS
 * OSS - Object Storage Server - software service that manages access to filesystem data (read, write, truncate, etc)
 * OST - Object Storage Target - storage device that holds the filesystem data (regular data files, not directories, xattrs, or other metadata)
 * PTLRPC - Portal RPC - A remote procedure call protocol layered over LNET

When is the next Major release?
We plan to tag and build Major releases of Lustre about every six months, the roadmap gives a high level idea of the current expectations

When is the next Maintenance Release?
There are multiple maintenance relesases per year but the exact timing can depend upon several factors (Linux distro releases, OpenZFS releases, important bugfixes). The Lustre Working Group is the best source of information about the latest status