[SGVLUG] Any VMware users out there?
Vincent Cordrey (SGVLUG)
vcordrey45704 at endlessknot.com
Wed Mar 25 11:33:40 PDT 2009
Actually, the biggest issue causing the need for separate hard disks is
the head movement BETWEEN the two partitions, or areas of the
disk where the base OS and the guest OS store their data.
Those head movements tend to cause additional latency and would
probably cause applications on both the base OS and guest OS's to
run fairly slowly (probably about 1/3 to 1/4 the speed) if there was
a reasonable amount of disk I/O.
To solve this problem, a solid state disk will have no such latency
issues, and could use only one drive. Basically, there's no penalty
for reading from or writing to a solid state disk in completely random
far flung regions of the storage. Where with a physical disk, moving
the head from one area to another, can be time consuming, especially if you
have two or more OSs trying to do that to different areas at the same
time--you'll get thrashing with the head constantly in motion jumping
back and forth to different areas of the disk.
I would be interested to know how folks have fared with solid state
disks in VM environments. My expectation is that they will work VERY
well, and suffer only minimal degradation with the increasing number
of guest OSs added. The curve should be fairly consistent until you
saturate the IO channel (unlikely) or the throughput of the solid state
disk controller electronics.
Specifically, I would expect it to behave with performance characteristics
in terms of response time statistics similar to half duplex Ethernet, and
have almost no noticeable bottle necking until you reach beyond 40%
of the ultimate bandwidth of the disk drive. Then, beyond that 40%, I
would expect a falling performance curve as measured from the point
of view of any one of the guest OS's which is actually requesting I/O.
Good food for thought!
> fyi -
> iirc, from a few VM presentations at various conferences:
> 1) Games which attempt to directly access the video card
> will have issues.... ( some games basically need to have
> admin level access, aka "root" level, to the hardware iirc )
> in fact
> 2) Any application which attempts to directly access
> SOME particular hardware on the system which do not
> have appropriate enough driver support for VMs will have
> issues. This can include bar code scanners, and other
> hardware essential to biz operations.
> to resolve performance issues:
> 1) RAM, lots of RAM
> ( thankfully, that's super cheap now.. :)
> would be nice to see more systems supporting
> 2) separate hard drives.
> many presenters had external mini-HDs with
> their laptops from which they ran the VMs,
> and recommended desktops which use VMs to
> have separate HDs for performance issues.
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