hammer upgrade changes md5 checksum

Matthew Dillon dillon at apollo.backplane.com
Mon Mar 16 19:15:12 PDT 2009

:Now I upgrade the /slave:
:  hammer pfs-upgrade /slave
:and get a different checksum:
:  cd /slave
:  tar cf - DIR | md5     # 3613c...
:If I downgrade again, I get the same checksum as before (9472f...).
:Hm, just curious why this happens and if this might be a bug?
:  Michael

    This is probably because HAMMER treats snapshots differently from
    live.  The mtime and atime will be locked to the ctime when accessed
    from a snapshot.  tar does not record atime, but I'm pretty sure it
    does record mtime.

    A slave is accessed as a snapshot.  The snapshot TID is the last synced
    TID.  A master is accessed live (if no @@<TID> extension is given).
    That's the difference.

    If you access the master using the slve's last-synced TID you should
    get the same md5.  This information is available in the pfs-status

					Matthew Dillon 
					<dillon at backplane.com>

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