[Discuss] How do Linux guys back up Windows?

[gaf at blu.org (Jerry Feldman)]

On 12/27/2012 09:59 PM, Edward Ned Harvey (blu) wrote:
>> From: discuss-bounces+blu=nedharvey.com at blu.org [mailto:discuss-
>> bounces+blu=nedharvey.com at blu.org] On Behalf Of David Kramer
>>
>>> 2. Performance of a VM is going to be less than that if it is native.
> This is not correct.  Well ... Sometimes it's correct, but sometimes guest VM's perform better than they would have if it were running on raw hardware.  Case and point, whenever the host OS offers any performance or other features that otherwise aren't available in the guest OS.  When I run virtualbox linux guests inside of solaris/openindiana hosts, ZFS makes the guest storage faster than it could have been natively.  Not to mention, backups are much faster thanks to snapshots.
>
You are correct. There are some cases where the guest OS does perform
better. Years ago, I was running an IBM mainframe (s370), and I tested
OS/VS1 native on payroll one night, The next day I had it running VM/370
with several users online, and we had to rerun payroll. Payroll ran
faster under VM370. One reason was paging. The OS/VS1 paging algorithm
was weak and used smaller page sizes than VM/370. We also found out that
spooling under VM/370 was much better even though this was a double
spooling situation. Another company presented a paper at a SHARE
convention showing how they could get much better throughput running
VM/370 and splitting their guest OS into 2 VMs, one for interactive
(using CICS) and one for batch. Additionally, some 370 models had some
assists in the firmware. One real advantage for us was since we migrated
from Burroughs that had dynamic device selection that IBM's systems did
not, we could assign additional virtual tape drives.

But, for things like gaming, virtualizing Windows probably affects the
performance, and the same with iTunes.

-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix
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