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[Linux-cluster] pool and LVM, and changes since 2000

In his 2000 OLS talk, Ken Preslan talks about some older software like
"pool" and "memexp".  I want to make sure I understand how things have
changed since 2000.  Are the following paragraphs correct?

  Pool is software that the GFS folks created before LVM was ready.
  LVM does volume management today, and pool is obsolete.
  One of the features of pool that he mentions is also in LVM:
  identifying physical block devices by their contents instead of
  their location.  The example he gives is of a SCSI drive in a
  fiber channel network, where adding a drive in one room can change
  the LUN of a drive in another room.  Pool allowed tracking of
  drives regardless of their location.  LVM does the same thing.

  The memexp locking module that was new at the time of the 2000 OLS
  talk was designed to use RAM exported by fancy storage hardware for
  coordinating locking.  A single node could stand in, though, taking
  the place of the fancy RAM-exporting storage hardware.  Today, most
  GFS installations use DLM instead.

  Preslan mentions that after acquiring a lock, a node must "heartbeat
  the drive" because the locking state is on the storage hardware.

How is that done these days?  Does a lock owner heartbeat the lock
master or does cluster management take care of this issue?

  Ed L Cashin <ecashin coraid com>

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