Re: [Xen-users] What are your bottleneck in using Xen solution?

[Luke S Crawford <lsc@xxxxxxxxx>]

howard chen <howachen@xxxxxxxxx> writes:
> Given that nowadays standard Dual Quad Core server is such popular,
> with Dual GB Ethernet, bundles of high capacity of SATA disks running
> as RAID 10.
> 
> What are the factors that prevent you from installing additional VM on
> an existing server?


I usually run out of ram before people start complaining of anything else
being slow, even with a single sata mirror.  Most of my systems are dual
socket quad core opterons (the oldest are 1.8Ghz bartons, the newer 
systems are 2.2Ghz Shanghai cores.)   My standard system has 32GiB ram.  
I have one box with 64GiB ram (and that one has two mirrors)  

yeah, as someone else said, the answer is 'it depends' -  but having extra 
ram covers a multitude of sins.  Sufficient disk cache, once a box is 'warmed 
up,' makes up for a slow disk, and slow cpu is usually more tolerable than 
hitting disk, as once you hit disk, performance falls off a cliff, even
with the 15K SAS disk that doesn't fit in my business model.  (now, things
change some if you can afford the fastest SSDs available, but hey,
I'm competing on price here.   Spinning disk is the only possibility... for
now.)

This, by the way, is why I use Xen and not OpenVZ or FreeBSD Jails, 
when I was using FreeBSD jails, (at the time, I was using 10K fibre
disk)   one heavy user would flush everyone else's disk cache, making
performance unacceptable.  

when the CPU is overloaded, the performance degradation is usually
more gradual, and more tolerable.  

I choose my hardware to maximize the amount of ram I can give for a
particular price.            

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