Xen users - Nov 2005 - Xen for network services (aka web/mail/dns etc)

Hi There,

We are looking to consolidate/upgrade our hosting platform equipment
early next year (Jan/Feb). Currently we have our main mysql server,
which runs dual Xeon EM64T processors, 4GB of RAM and a 500GB RAID 5
array. The rest of the equipment is odds and ends - the reason why we
are looking to upgrade.

Within our platform, we run apache/php/asp ,mysql ,mail
(SMTP/POP/IMAP) and dns servers which we provide to our wholesale
clients.

I was just down the path of configuring up multiple IBM xseries 306
rack servers to replace all by the mysql server (above) and then...
Xen.

My question is: we have a good mysql server which is underutilised...
could this server be changed to a Xen server and perform well given
the processor type?

If we were to leave this as the mysql/storage server, and look at
purchasing some new gear for a xen server  (to replace the other 4-6
''real'' servers) - what are the suggestions on hardware? We use
debian
on all servers.

Thanks

Simon

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So long as the system is up to the CPU and IO load you''ll be placing on
it (and without knowing your load, it''s hard to say much), you
shouldn''t
have trouble. However, a few pieces of advice:

- Move your MySQL instance into a DomU, even if it''s not as convenient 
as you''d like.

- If you aren''t using LVM, seriously consider using it; it makes
storage
management much more reasonable.

Have a nice, long maintenance window -- and practice first on a 
non-production machine.

If you''re CPU bound, consider moving to dual-core processors. (If
you''re
I/O-bound, this obviously won''t help -- so consider your load and try
to
be sure you *won''t* be I/O-bound).

We use Gentoo on our Dom0s and a mix of Gentoo and SLES9 on our DomUs, 
so I can''t give any advice regarding Debian.


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On 12/1/05, Charles Duffy <cduffy@spamcop.net> wrote:
> So long as the system is up to the CPU and IO load you''ll be
placing on
> it (and without knowing your load, it''s hard to say much), you
shouldn''t
> have trouble. However, a few pieces of advice:
The load on the current mysql server is -0.1 average.
> - Move your MySQL instance into a DomU, even if it''s not as
convenient
> as you''d like.
I have been thinking of leaving this as a completly seperate server
and purchasing new equiptment for running Xen on. I have been looking
at IBM xSeries 446 rack gear with dual 3.0Ghz Xeon ''Irwindale''
processors.

In looking at new gear? What would be the best processors to concider?
> - If you aren''t using LVM, seriously consider using it; it makes
storage
> management much more reasonable.
Yep - will do. We are tesing with disk images at the moment (only been
installed for a day or so - just to play with).

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> - If you aren''t using LVM, seriously consider using it; it makes
storage
> management much more reasonable.
What is the optimum storage ideal here? Currently we have a RAID 5
disk with a fair amount of space available. Also: Can you store your
domU partitions on a NAS or something?

Simon

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On 12/1/05, John R. Shannon <john@johnrshannon.com> wrote:
> I''m in the middle of a server consolidation project simular to the
one you''re
> comtemplating. In my case, I procurred new hardware to ensure that my old
> servers could function during the process if setting up and testing the new
> Xen-based server. You may have simular considerations.
Yes - i guess we do!
> My plans calls for 7 user domains plus domain0. I have three user domains
> completed and have the Xen-domain based http/https server online. A
supplier
> shipped one SCSI disk, instead of two, so I''m awaiting the arrival
of a
> second disk to complete the project.
By user domains, i take it that this is a domU? (sorry - new to this).
If so, we would be looking at 5 user domains. 1: web/ftp 2: dbmail 3:
smtp 4: pop/imap 5: dns on a single server (server1).

I would keep my mysql server as a separate server... but could make
this server a Xen server (server2) as well, with the 1 domU running
mysql. This could also be used to move domU''s from sever1 if need be
(fail over?). Thoughts here?

Also, what about backup implications of each domU, how is this best
achieved? A third server to backup all the domU''s from each server1
and server2?

Any input is greatly appeicated.

Regards,

Simon

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Simon wrote:
> On 12/1/05, Charles Duffy <cduffy@spamcop.net> wrote:
> 
>>So long as the system is up to the CPU and IO load you''ll be
placing on
>>it (and without knowing your load, it''s hard to say much), you
shouldn''t
>>have trouble. However, a few pieces of advice:
> 
> The load on the current mysql server is -0.1 average.
Right, but that''s a completely different workload than it''s
going to
have later.
>>- Move your MySQL instance into a DomU, even if it''s not as
convenient
>>as you''d like.
> 
> I have been thinking of leaving this as a completly seperate server
> and purchasing new equiptment for running Xen on. I have been looking
> at IBM xSeries 446 rack gear with dual 3.0Ghz Xeon
''Irwindale''
> processors.
> 
> In looking at new gear? What would be the best processors to concider?
We''re an AMD shop, and very happy to be so. Any advice I gave you wrt 
processors would be heavily slanted in that direction. (There are the 
power considerations, of course -- and from what we understand, AMD''s 
dual core architecture performs significantly better than Intel''s).
> What is the optimum storage ideal here? Currently we have a RAID 5
> disk with a fair amount of space available. Also: Can you store your
> domU partitions on a NAS or something?
Whatever works for you -- depends on your workload. Yes, you can keep 
the storage in question on a NAS. If it''s iSCSI, AOE or otherwise at a 
block device level (rather than something akin to NFS), I recommend 
mounting the devices on the Dom0 and incorporating that into your 
volumes which get exported to the DomUs.

Having your storage be on a NAS should make migrating your DomUs around 
between Xen servers (for hardware maintenance or whatnot) easier.


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Simon wrote:
> I have been thinking of leaving this as a completly seperate server
> and purchasing new equiptment for running Xen on. I have been
> looking at IBM xSeries 446 rack gear with dual 3.0Ghz Xeon
> ''Irwindale'' processors.
>
> In looking at new gear? What would be the best processors to
> concider?
You might ask about the ''Cedar Mill'' line of Intel processors
as they
reportedly have the Vanderpool features.

- --
Some days it''s just not worth chewing through the restraints...
Mark D. Foster, CISSP <mark@foster.cc>  http://mark.foster.cc/

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> > I have been thinking of leaving this as a completly seperate server
> > and purchasing new equiptment for running Xen on. I have been
> > looking at IBM xSeries 446 rack gear with dual 3.0Ghz Xeon
> > ''Irwindale'' processors.
> >
> > In looking at new gear? What would be the best processors to
> > concider?
>
> You might ask about the ''Cedar Mill'' line of Intel
processors as they
> reportedly have the Vanderpool features.
The main thing im worried about at the moment is the SMP capacity of
servers and Xen. if im going to be depoying in feb 2006 (gives me a
couple of months to test etc).. Should i be working with Xen 3?

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> The main thing im worried about at the moment is the SMP capacity of
> servers and Xen. if im going to be depoying in feb 2006 (gives me a
> couple of months to test etc).. Should i be working with Xen 3?
You should at least evaluate Xen 3, since the 2.0.x series is not actively 
developed any more.  Xen 3 will give you SMP capacity you want, as well as 
various other funky stuff.

Cheers,
Mark

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On 12/2/05, Mark Williamson <mark.williamson@cl.cam.ac.uk> wrote:
> > The main thing im worried about at the moment is the SMP capacity of
> > servers and Xen. if im going to be depoying in feb 2006 (gives me a
> > couple of months to test etc).. Should i be working with Xen 3?
>
> You should at least evaluate Xen 3, since the 2.0.x series is not actively
> developed any more.  Xen 3 will give you SMP capacity you want, as well as
> various other funky stuff.
Thanks Mark, I am installing now :)

On the subject of hardware, i am looking at the xSeries 336 from IBM
(as discussed already). These have dual xeon''s. 1 of the above (to
begin with), 4GB of RAM and RAID1 for the host OS. The AOE EtherDrive
for storage for the domU''s (giving the ability to move a domU from
server to server?) - is this overkill?. We also would have our current
2 x Xeon server (custom build), giving 2 servers in total.

These are the domUs that i would want to have:

- apache/php domU
- apache/asp(sun asp) domU
- dbmail/imap/pop domU
- smtp-in/av/spam domU
- smtp-out/av domU (for autheticated clients)
- mysql domU (for apache servers)
- mysql domU (for dbmail and mydns)
- dns (mydns) domU

What would be the best way to spread the domUs across the available servers?

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> Thanks Mark, I am installing now :)
>
> On the subject of hardware, i am looking at the xSeries 336 from IBM
> (as discussed already). These have dual xeon''s. 1 of the above (to
> begin with), 4GB of RAM and RAID1 for the host OS.
Nb if you want to fully use the 4GB you''ll want to install x84_64 Xen
(or PAE
Xen if you really don''t want to use x86_64).  This is because of
limitations
of the PC platform.  If you ever extend the memory further then you''ll 
certainly want to be using a version of Xen with full addressing capability.

Bear in mind that for Xen-native guests, you need to match kernel and Xen 
addressing mode: i.e. PAE guest on PAE Xen, 32-on-32, 64-on-64 - no mixing 
them up.  This doesn''t apply to fully-virtualised guests, which will
run
under a Xen of equal or greater addressing size.
> The AOE EtherDrive 
> for storage for the domU''s (giving the ability to move a domU from
> server to server?) - is this overkill?.
You can set up some software-based network storage solution (e.g. enbd) - test 
that and see if it performs well enough for your workload.
> - apache/php domU
> - apache/asp(sun asp) domU
> - dbmail/imap/pop domU
> - smtp-in/av/spam domU
> - smtp-out/av domU (for autheticated clients)
> - mysql domU (for apache servers)
> - mysql domU (for dbmail and mydns)
> - dns (mydns) domU
>
> What would be the best way to spread the domUs across the available
> servers?
Depends how highly loaded they are.  If you set up networked storage, you can 
always migrate them to a less loaded machine.

Cheers,
Mark

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