raid5 > raid 0=1 ?

Mirror the stripes better than striping the mirrors ?

bsd better than linux ?

2.2 better than 2.4 ?

Would somebody please post some proof (and some details?) !

I have posted some of my results with linux software raid at
http://www.quadratic.net (see the "Wed Aug 29 09:45:21 EDT 2001" entry )

Among this community I think that it is very important to show your work.

ON that note,

We have a "Really Big UPS"(tm), so I feel completely comforatble using a ram
disk for queues, in fact I played with linux 2.2 and found the the limit to
a single ram disks size was 525 Megs. Linux 2.2 has a limit of 2 GB for ram
so we found a nice balance with 3 X 525 Ram disks and ~500 Megs of system
memory. We run multiple instances of postfix. We used a total of nine
instances each bound to a single physical interface each with their own
queue dirs (3 to a ram disk). We found that linux got confused with 12
interfaces. This machine has 9 ethernet cards and 9 private IPs (mapped on
the firewall to 9 public IPs). This presents some routing fun but that's a
network issue not a postfix issue.

We found that (smart) remote machines would throttle back on us if we sent
too much mail as fast as we could. We got around that with many interfaces.
Where before we could send 900 message to a host before seeing the transfer
rate go down, with 9 interfaces that number grew to ~8000. It eventually
slowed to a trickle but we got more out faster.

The setup is working well for us. We have a total of 7 of these type of
machines churning away.

and look at that I have no reports to show for it. Aren't I just a big
hipocrit ? bleh...

david

---
David Thornton
ATT Canada - Internet Data Centre Services
Me: dthorntoncorp.attcanada.ca 905-896-6263
My Department: Internet Data Centre Services supportboaw.net 905-896-6386
My Supervisor: Mike Molson mmolsoncorp.attcanada.ca 906-896-6268 
> -----Original Message-----
> From: Craig Sanders [mailto:castaz.net.au]
> Sent: Thursday, September 27, 2001 5:41 AM
> To: postfix-userscloud9.net
> Subject: Re: 1.000.000 email posted in a single delivery process
> 
> 
> On Thu, Sep 27, 2001 at 11:37:46AM +0300, Liviu Daia wrote:
> > On 26 September 2001, Alexander <mlambrosa.it> wrote:
> > [...]
> > > Title: the best mode to deliver 1.000.000 email messages 
> (recipient
> > > are ALL different and email are ALL different) in few 
> hours during a
> > > single delivery session.
> > >
> > > You suppose to have a SMP Linux server (i.e. dual P-III 
> 800 Mhz, 512
> > > MB Ram, SCSI Raid 5, kernel 2.4.9 and RaiserFS) and a 
> good internet
> > > connection (4 Mbit/sec full bandwidth) and a fast DNS 
> server near me.
> 
> it was mentioned earlier in the thread that the queue size probably
> wouldn't exceed 1GB because the messages were quite small (even though
> there's a million of them in the queue).
> 
> in that case, a 2GB sold-state disk would be a good idea for the queue
> directory. can't get faster than that for disk I/O. formatting it with
> reiserfs would be good too.
> 
> >     Wietse already explained how to setup Postfix for best 
> performance.
> > Here's an additional checklist, mainly for the rest of the system:
> > 
> > - if possible, use OpenBSD or FreeBSD with softupdates rather than
> >   Linux;
> 
> alternatively, configure and use linux properly rather than believe
> propaganda.
> 
> > - if you insist on using Linux, use a 2.2.x kernel, not a 2.4.x one,
> > and turn OFF the swap; buy more RAM if you feel you're 
> running out of
> > it;
> 
> 2.4.x kernels are perfectly adequate, indeed much better than 
> 2.2.x kernels.
> 
> and there's no need to turn off the swap. 
> 
> adding RAM is always a good idea.
> 
> > - use RAID 0+1, not 5, and (if you have that choice) mirror 
> the stripes
> >   instead of striping the mirrors;
> 
> my testing a few months ago proved that RAID5 is significantly faster
> than RAID0+1 for the kind of disk loads you see on mail servers.
> 
> the tests were performed using the exact same hardware, and same
> software, on the same machine - dual P3-866 with 512MB RAM, hardware
> raid card with 32MB non-volatile cache, and 6 x 18GB IBM drives.
> 
> RAID0 is certainly faster than anything else, but RAID1 or RAID0+1 is
> slow. think about how it works - raid0 is striping which is 
> fast. raid1
> is mirroring which is slow, every write has to be mirrored to 
> the mirror
> drive...so by striping several raid1 arrays together you end up with
> striped access to slow devices.
> 
> still, a solid-state-disk would make this a moot point.
> 
> 
> > - use ext2; Xfs and Jfs are not yet ready for prime time, and
> > everything else is slower than ext2 for mail handling;
> 
> ext2 would be one of the worst choices for a mail server's filesystem.
> 
> xfs is reliable and ready for prime-time in my experience. 
> i'm using it
> on several low volume mail servers, as well as several web 
> and postgres
> servers. i also use it on my amanda backup server (to get 
> around the 2GB
> file size limit in ext2).
> 
> it's not as fast as reiserfs for mail loads, but it's a LOT 
> faster than
> ext2.
> 
> reiserfs also works reliably, and i've been using it on 
> production mail
> servers for over a year. reiserfs is also much faster than 
> anything else
> for the kind of disk i/o you see on a postfix server - lots of little
> files being created, renamed, and deleted.
> 
> dunno about jfs or ext3. haven't used either of them yet. no 
> need to, so
> far.
> 
> 
> > - install a caching DNS on the SAME machine as the mail 
> server, a nearby
> >   one is not good enough; use djbdns for that instead of 
> bind; turn off
> >   logging for lookups, and give it plenty of memory to keep 
> the cache;
> 
> yep.  caching dns is good.  don't think i'd use djbdns though.
> 
> > - if you trust your UPS, turn off sync writes to the queue
> >   ("chattr -R -S /var/spool/postfix")
> 
> only necessary if you run ext2 for your queue directory - 
> which is a bad
> idea if performance is important to you.
> 
> craig
> 
> -- 
> craig sanders <castaz.net.au>
> 
> Fabricati Diem, PVNC.
>  -- motto of the Ankh-Morpork City Watch
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