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A
simple example:
OpenSMS
is a peer to peer, policy driven storage management tool.
The basic configured unit is a managed filesystem. Files
created or updated in a managed filesystem can have one
or more sets of policy applied in quasi real time.
A
simple (and already supported) example would be mirroring
to another filesystem (local or remote). When files are
created or updated, after they stop changing, they are
automatically copied to the mirror filesystem. Having
a separate filesystem as the mirror target has some dramatic
benefits over block-level mirroring.
To
extend the example, you could configure the mirror filesystem
to automatically mirror itself to tape (or to another
filesystem, or both...). Then every file created or updated on the first filesystem would be mirrored to
the second filesystem...and then written to tape.
Notice
that both the source and target filesystems are now running
event-driven policy. The OpenSMS framework gives you tremendous
flexibility with capabilities like these:
- You
can configure an unlimited number of policy-driven tiers.
- A
single tier can run multiple "policy engines",
such as copying both to a mirror filesystem and to tape,
or copying to multiple mirror filesystems.
-
You can control which files are collocated together
on tape, via file type, ownership, or other criteria
you define.
- You
can "punch a hole" in any disk tier, such
that the file is visible but the space is freed until
the file is accessed, at which point the data is re-staged
from another tier (disk or tape).
- If
a file is not on disk, but it is on tape, "aware"
applications can access the data directly from tape
(very powerful for sequentially-accessed data) rather
than "faulting" the data back to disk before
accessing it.
For
its tape interface, OpenSMS uses its sister project, OpenTMS.
Released in 2004 to the open source community by StorageTek
after many years as a commercial product, OpenTMS provides
mainframe-class abstraction of tapes and tape automation
into a usable API.
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