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From: jon_at_kollegiegaarden.dk
Date: Sun 09 Nov 2003 - 22:46:39 GMT

On Sun, Nov 09, 2003 at 03:12:13PM -0500, Matthew Nuzum wrote:

it is annoying that your mail program does not wrap long lines.

> We have been working on an OpenMosix cluster in the computer club at
> the school where I'm taking classes now. I've found that the server
> applications that I typically use do not benefit from openmosix. The
> applications commonly fall into either of two categories:
> a) I/O bound applications that only slow down when migrated to a different
> node on the cluster, or
> b) Applications that are incompatible with Mosix for various reasons
> (threaded, shmem, device dependent etc.) such as Database software,
> Apache and other server processes.

true, I/O bound processes are not good for migrating, but not all
has that kind of processes. And even if they do... Gbit networking
is cheap, and is certainly faster than most harddrives. So, fill a
server with several harddrives, run raid, and export it through the
network, and you will get a better throughput than you would on a
single drive, and probably even a 2 disk mirror/stripe.

one day those processes might be migrateable.

> I think the audience of people who can legitimately benefit from
> a combined vserver/mosix installation is rather small.

I'm not so sure, i think that once the technology is there, alot
of people would want it. They just dont know it yet. Besides even
if it is a small ammount of people, why not allow them to have this

> For those that have heavily loaded servers, why not just put fewer
> vservers on a server? If 6 is too many, just do 4 or 5. If you
> have extra boxes with spare cpu cycles, put the vserver there.

if you can NOT tolerate downtime, then it is currently card to
migrate the vservers.
I imagien a cluster of machines, which only power on when needed.
This saves electricity and heat. The actual data is located on a
server, because disks are slower than network. Thus, the machines
boot fast, and then you can more the "vservers" to that new physical
machine. I can imagien this is usefull for hosting providers, because
they can automaticaly power up that extra 8-way opteron with 16G ram
the hosting provider has for backup purposes. They have 2. One runs the
vservers for customers, and the other is a spare, used if the other
fails, or is too small. The spare is normaly shut down to save
electricity and heat. (it's located in california ;-P

One of their customers is thinkgeek. Then suddently thinkgeek is
slashdottet, and normaly their vserver would crawl to a halt,
because they ordered a vserver with these limits 10%cpu, 1G memory.

However, the hosting provider has a special option for their customers
they can choose a disaster package, that allows the customers vservers
to suddently use ALOT MORE COMPUTER-RESOURCES. So, the hosting provider
power on the extra spare 8-way opteron, and migrate the thinkgeek-vserver
to that machine, running ONLY that vserver, and gives it all the cpu
and memory it want.

The result is that thinkgeek captures all those extra 324723489273434
orders, rather than dropping them because the vserver is not powerfull

All this happens without anyone noticing anything, and while the machine
is running. No downtime.

> Honestly, if your mailserver setup is too slow, I'm certain you can
> get better performance by switching from IDE disks to SCSI. In my
> recent tests, I/O tasks on IDE drives kept the CPU at about 53%
> utilization. Same tests on SCSI disks used only 14% utilization
> with the I/O processes taking significantly less time to complete
> on the SCSI. That was a system with a single IDE drive compared
> to the same system with a single SCSI drive.

Just because this situation might not use vserver/openmosix, does
not mean other situations can not use it.

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