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Lustre 2.0

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(Replication)

Revision as of 09:15, 9 April 2009

Lustre 2.0 introduces several significant new features and improved system functionality. This page provides descriptions of these features and lists the benefits offered by upgrading to Lustre 2.0.

Contents

Changelogs

Changelogs record events that change the filesystem namespace or file metadata. Events such as file creation, deletion, renaming, attribute changes, etc. are recorded with the target and parent file identifiers (FIDs), the name of the target, and a timestamp. These records can be used for a variety of purposes:

  • Record recent changes to feed into an archiving system.
  • Use changelog entries to exactly replicate changes in a filesystem mirror.
  • Set up "watch scripts" that take action on certain events or directories. Changelog record are persistent (on disk) until explicitly cleared by the user. The are guaranteed to accurately reflect on-disk changes in the event of a server failure.
  • Maintain a rough audit trail (file/directory changes with timestamps, but no user information).

These are sample changelog entries:

2 02MKDIR 4298396676 0x0 t=[0x200000405:0x15f9:0x0] p=[0x13:0x15e5a7a3:0x0] pics
3 01CREAT 4298402264 0x0 t=[0x200000405:0x15fa:0x0] p=[0x200000405:0x15f9:0x0] chloe.jpg
4 06UNLNK 4298404466 0x0 t=[0x200000405:0x15fa:0x0] p=[0x200000405:0x15f9:0x0] chloe.jpg
5 07RMDIR 4298405394 0x0 t=[0x200000405:0x15f9:0x0] p=[0x13:0x15e5a7a3:0x0] pics 

The record types are:

MARK internal record keeping
CREAT regular file creation
MKDIR directory creation
HLINK hardlink
SLINK softlink
MKNOD other file creation
UNLNK regular file removal
RMDIR directory removal
RNMFM rename, original
RNMTO rename, final
OPEN file opened for write
CLOSE file closed for write
IOCTL ioctl on file or dir
TRUNC regular file truncated
SATTR attribute change
XATTR extended attribute change
UNKNW unknown op

FID-to-full-pathname and pathname-to-FID functions are also included to map target and parent FIDs into the filesystem namespace.

Why should I upgrade to Lustre 2.0 to get it?

Changelogs offer these benefits:

  • File/directory change notification
  • Event notification
  • Filesystem replication
  • File backup policy decisions
  • Audit trail

Additional Resources

For more information about changelogs see:

Replication

The replication feature makes a (qualified) replica of a Lustre filesystem on another filesystem target. The target may be another Lustre filesystem or any other filesystem. This features differs from existing backup/replication/synchronization systems primarily in that it is designed to avoid walking the namespace tree, which for very large filesystems becomes unreasonably time-consuming. Replication is based on server changelogs, and uses the information in those logs to determine which directory and file operations to execute on the replicated system. The replicated filesystem is an exact copy of the namespace of the original system as of a given point in time. However, the replicated filesystem it is not a snapshot of the original filesystem in that its contents may differ from the contents of the original filesystem. File contents of the replica will be the contents of the file at the time the data transfer of that file took place.

Why should I upgrade to Lustre 2.0 to get it?

Replication offers this benefit:

  • Namespace-coherent duplication of large filesystems without walking the filesystem.

Additional Resources

For more information on replication, see:

HSM

The HSM feature provides several mechanisms to interface with an external HSM system. External components include the policy engine, and file storage, retrieval, and removal methods. The external components are expected to run in userspace. Internal components include Lustre metadata extensions, and a distributed coordinator/agent architecture to call the file storage methods. Policy engine input and feedback is expected to occur primarily though the changelog. In its initial implementation, the HSM feature uses HPSS for the external components.

Why should I upgrade to Lustre 2.0 to get it?

HSM offers these benefits:

  • Cost-effective filesystem expansion
  • Potential for backup policies in the policy engine

Additional Resources

For more information on HSM, see:

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