HAMMER and RAID question

Matthew Dillon dillon at apollo.backplane.com
Thu May 27 11:03:42 PDT 2010

:let me start this first by admitting that I know next to nothing about 
:designing and implementing file systems.  It is just that I've been 
:naively thinking about things.
:It is my understanding that code has been added to reblock files during 
:production use.  Could this not also be the foundation of RAID-like 
:functionality? If blocklists had a notion that a block needs to exist on 
:at least two physical volumes, mirroring would already be there.
:Or is this too far away from what HAMMER does internally these days?
:Thank you,
:  Konrad Neuwirth

    Theoretically the B-Tree could be used to list multiple copies of
    a data block but it would really complicate the filesystem.  HAMMER's
    media structure is designed for replication across distinct copies
    of the filesystem rather than trying to maintain redundancy within
    a single copy of the filesystem.

					Matthew Dillon 
					<dillon at backplane.com>

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