Lustre 1.6 Operations Manual

opencache
Orphan objects
Orphan handling
OSC
OSD
OSS
OSS
OST
A cache of open file handles. This is a performance enhancement for NFS.
Storage objects for which there is no Lustre file pointing at them. Orphan
objects can arise from crashes and are automatically removed by an llog
recovery. When a client deletes a file, the MDT gives back a cookie for each
stripe. The client then sends the cookie and directs the OST to delete the stripe.
Finally, the OST sends the cookie back to the MDT to cancel it.
A component of the metadata service which allows for recovery of open,
unlinked files after a server crash. The implementation of this feature retains
open, unlinked files as orphan objects until it is determined that no clients are
using them.
Object Storage Client. The client unit talking to an OST (via an OSS).
Object Storage Device. A generic, industry term for storage devices with more
extended interface than block-oriented devices, such as disks. Lustre uses this
name to describe to a software module that implements an object storage API
in the kernel. Lustre also uses this name to refer to an instance of an object
storage device created by that driver. The OSD device is layered on a file
system, with methods that mimic create, destroy and I/O operations on file
inodes.
Object Storage Server). A system that runs an object storage service software
stack.
Object Storage Server. A server OBD that provides access to local OSTs.
Object Storage Target). An OSD made accessible through a network protocol.
Typically, an OST is associated with a unique OSD which, in turn is associated
with a formatted disk file system on the server containing the storage objects.
P
Pdirops
pool
A locking protocol introduced in the VFS by CFS to allow for concurrent
operations on a single directory inode.
A group of OSTs can be combined into a pool with unique access permissions
and stripe characteristics. Each OST is a member of only one pool, while an
MDT can serve files from multiple pools. A client accesses one pool on the the
file system; the MDT stores files from / for that client only on that pool's OSTs.
Glossary-8 Lustre 1.6 Operations Manual • September 2008