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From: Paul Sladen (vserver_at_paul.sladen.org)
Date: Mon 30 Dec 2002 - 10:51:54 GMT

On Sun, 29 Dec 2002, Dinesh Mistry wrote:
> Linux pretty much uses all the memory you throw at it so top is not very

Linux `uses' any spare memory for disk/file cacheing. top (press "M") and
ps will show you what is using memory. The show socket-answering problem I
don't think is specifically vserver related, although it may be large-usage
related. (eg, best example might be the 30-second delay that some IRC
servers have when people use the main 6667 port).
> Secondly is there some sort of 'rule of thumb' to figure out how many VPS's
> you can run on a specific type of server CPU/MEM type calculation?

[Exploitive commercial-angle to this question ignored. ;-)]

Well, DSVR appear to be stacking 75 per machine. Idaya were blagging about
250 per host (limit on /proc only being mountable 256 times). The SW-Soft's
demo server was filling a /24's worth (so 250 again).

It is a question of contentions--look at it as 1GHz of CPU on a 1:100
contention ratio--if the machine is normally sitting there with a 0.01%
CPU usage then you can see there isn't going to be a problem.

It's when people start running spamassassin, efficiently written (database
wise) high-traffic PHP sites or distributed.net--that people will notice.

For this many on one server, you really need to be using the unification.
Both to save the disk-space (300MB base install * 100 is 30GB). But also
reducing the in-memory footprint. Having 1 copy of a 1MB Apache binary is
better than 100 copies; 1 MB image of bash is better than 1000 copies...

Linux's Copy-on-Write memory allocation is truly great! :-)

However, I'm not really interested in the highly-identical reseller
machines--I'm using vserver to run independent servers (``server
consolidation'') and I would estimate 20-30 per host leaving *plenty of
resources* all around. Although one CPU-hour of kernel compiling, per
machine, per day is still major overkill!

Maybe a question of how many phat [reliable] SCSI disks you can afford.

Hope this wasn't too unhelpful. I don't think there is a hard and fast
rule. It depends who your customers are, if they all want to play QuakeIII
over an X-session you might have a problem.


PS. Make sure you have *plenty* (GB's worth) to page-out the less-accessed
     memory to.

Nottingham, GB

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