[CentOS] Large file system idea

Sat May 17 21:10:31 UTC 2014
SilverTip257 <silvertip257 at gmail.com>

On Sat, May 17, 2014 at 1:00 PM, Steve Thompson <smt at vgersoft.com> wrote:

> 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.
>

Right, DRBD is no longer available from the CentOS Extras repo (like it was
in EL5).


>
> 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.
>

Ah, good point.


-- 
---~~.~~---
Mike
//  SilverTip257  //