[CentOS] Large file system idea
Steve Thompson
smt at vgersoft.com
Sat May 17 17:00:05 UTC 2014
On Sat, 17 May 2014, SilverTip257 wrote:
> Sounds like you might be reinventing the wheel.
I think not; see below.
> DRBD [0] does what it sounds like you're trying to accomplish [1].
> Especially since you have two nodes A+B or C+D that are RAIDed over iSCSI.
> It's rather painless to set up two-nodes with DRBD.
I am familiar with DRBD, having used it for a number of years. However, I
don't think this does what I am describing. With a conventional two-node
DRBD setup, the drbd block device appears on both storage nodes, one of
which is primary. In this case, writes to the block device are done from
the client to the primary, and the storage I/O is done locally on the
primary and is forwarded across the network by the primary to the
secondary.
What I am describing in my experiment is a setup in which the block device
(/dev/mdXXX) appears on neither of the storage nodes, but on a third node.
Writes to the block device are done from the client to the third node and
are forwarded over the network to both storage servers. The whole setup
can be done with only packages from the base repo.
I don't see how this can be accomplished with DRBD, unless the DRBD
two-node setup then iscsi-exports the block device to the third node. With
provision for failover, this is surely a great deal more complex than the
setup that I have described.
If DRBD had the ability for the drbd block device to appear on a third
node (one that *does not have any storage*), then it would perhaps be
different.
Steve
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