Date: Mon, 23 Sep 1996 01:31:47 -0400 (EDT) From: Brian Tao <taob@io.org> To: FREEBSD-ISP-L <freebsd-isp@freebsd.org> Subject: Thoughts on a news server cluster Message-ID: <Pine.NEB.3.92.960923003632.24621M-100000@zap.io.org>
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The stuff I've been posting about hardware RAID products will
ultimately lead to the installation of a news server cluster. I've
been running fairly happily so far on a single P133 with 128MB, 3
NCR53810 controllers and 9 drives. No RAID, no ccd... just different
drives mounted at different points in the filesystem. The concurrency
is actually fairly decent, looking at iostat.
Anyhow, management has decided they want something more robust and
survivable, and that has led me down the path of redundant and
high-availability hardware without having to switch to some commercial
OS vendor. ;-) I've read a lot of discussion on building scalable,
reliable news server configurations. I'd like to know if anyone has
some wisdown to share on the FreeBSD specifics.
For example, someone mentioned that ccd did not appear to be all
that stable in -current. Would using 2.1.5-RELEASE be better?
Another thread mentioned that heavy NFS client activity causes
instability. Should I then avoid NFS altogether and pay a premium for
a local disk subsystem for each server?
This is the configuration I'm looking at. There will be three
PPro200 servers on a 100MB Ethernet segment. One will be dedicated to
incoming and outgoing feeds. The other two will be for readers.
The feeder server will have 4x2GB of local storage, holding about
2 days of news. It will handle all transactions with other servers
and not have to deal with NNRP reading or posting. One of its feeds
will be to the primary reader server. This reader server will be a
full news server in its own right, except that it has just the one
single upstream feed. I shouldn't have to mess around with XREPLIC or
NFS-mounting a huge spool off a busy feeder server.
The primary reader server will have 16x2GB drives, RAID 5 with hot
spares, two fast/wide controllers, 8 drives per controller. It
exchanges articles with the main feeder server as well as accepting
NNRP connections. I figure with just a single feed, I should be able
to avoid the problem of long newsreader startup delays because innd is
blocked on one of its connections. Secondary reader servers will
simply NFS-mount the spool as read-only and run in.nnrpd -S out of
inetd.
With the sharedactive patch, each 256MB reader server should be
able to handle 500 to 600 readers at once, based on my experiences
with my current news server. 128MB on the feeder server should be
more than enough for a few dozen feeds. This setup can then be
replicated to serve different geographical regions, with only the
feeder servers exchanging traffic to save on WAN bandwidth.
Any caveats I should look out for, especially with NFS and ccd?
Any other recommendations (besides getting more RAM ;-))? Have there
been any significant improvements to the AHA-2940UW driver in 2.2 that
isn't in 2.1.5?
--
Brian Tao (BT300, taob@io.org, taob@ican.net)
Senior Systems and Network Administrator, Internet Canada Corp.
"Though this be madness, yet there is method in't"
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