No database server product of which I am aware will "work" properly when the
database resides on a remote filesystem. There is a *vast* difference between
a "remote file system" and a "local file system on a remote block device".
There is no difference between a "remote block device" known as a Hard Disk
that is remotely attached via a SCSI/SATA/PATA/IDE/MDM cable on which the Local
Computer creates a local filesystem for its own exclusive use, and a "remote
block device" that is attached via iSCSI or Fiber Channel on which the Local
Computer creates a local filesystem for its own exclusive use, except for the
length of the cable connecting the "Local Computer" to the block storage device.
That is to say there is no difference between a block device (such as a
physical hard disk) attached to the computer via a 1 foot SCSI cable and an
iSCSI LUN where the iSCSI block device is located on a different plant, other
than the latency of the command/response. In both cases you are using a
This is vastly different from mounting a "remote shared filesystem" from
another computer, whether that computer is located in the next rack slot or
located on another planet.
The confusion stems from the ill-advised usage of the inaccurate term "Network
Attached Storage" by the ill-educated to refer to both "Remote Block Storage
with a Local Filesystem" and "Remote Shared Filesystem", and the propensity of
(some) of those hearing (or reading) the terms to make inappropriate
assumptions about the meaning of the terms without understanding the
consequences of those assumptions.
Practically every device connected to the Internet qualifies as "Network
Attached Storage" and from that perspective, the Internet is just a great big
"Storage Area Network".
Neither of those terms have anything to do with whether the filesystem is local
or remote. And the ability to create a "snapshot" does not require a Remote
File System, nor does it require a Local File System. In fact, it is
completely independent of where the Filesystem is locatedhow it is attached, or
the physical storage back-end.
> * R. Smith:
> > Enterprise DBs have servers on the same machine as the Files they
> > access, they do not actually use the network file-system to access the
> > DB data-files over the network from multiple clients, or even servers
> > (unless the DBs are partitioned so and ONLY accessed by the single
> > process so locking is permanent and moot).
> Deployments vary considerably. A lot of enterprises use snapshotable
> storage for databases as well, just as an option in case upgrades need
> to be rolled back.
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