Mailinglist Archive: opensuse (3156 mails)

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Re: [opensuse] Re: [OT] vmware and fake scsi devs
  • From: Aaron Kulkis <akulkis00@xxxxxxxxxx>
  • Date: Wed, 05 Dec 2007 19:12:38 -0500
  • Message-id: <47573E76.2070501@xxxxxxxxxx>
Chris Worley wrote:
On Dec 4, 2007 11:49 AM, Aaron Kulkis <akulkis00@xxxxxxxxxx> wrote:
Chris Worley wrote:
On Dec 4, 2007 10:22 AM, Jc Polanycia <JC.Polanycia@xxxxxxxxxxxx> wrote:
Off topic, as I seldom partition anything (unpartitioned drives
perform best), but, you're setting yourself up for disaster using LVM
(any corruption to the LVM layer is not recoverable... you'll loose
everything... been there done that), and the performance is poor, and
MD RAID5/6 devices can be grown (add more disks).

Chris

Fair enough. I appreciate the input because I haven't run across any
real-world stories about LVM corruption. I have personally encountered
corruption problems with RAID5/6 as well as problems with decreased
performance as a RAID5 structure gets more members added to it.
I saw some RAID6 issues last year, so I use RAID5... but recent tests
have shown MD RAID6 as solid.

"Decreased performance as more members get added to it"? Bull!!! I'm
guessing you have another bottleneck that has led you to this
conclusion.

While the performance increase doesn't scale linearly as disks are
added (some CPU verhead is added with each additional drive), the more
disks, the better the performance. I'm sure there is some Amdahl's
law limit to the increased performance scalability, but I run RAIDS up
to 12 drives, and see performance added w/ each new member.

You're hallucinating. That defies basic information theory.

Your assertion is akin to suggesting that you power your
computers with a perpetual motion machine (despite the
fact that such would violate the 1st, 2nd, and 3rd laws
of thermodynamics).

Amdahl's law defies "Information theory"? How so?

If you've got one disk that can perform at 70MB/s on a 320MB/s bus,
then on that bus you should be able to stripe at least four drives
with less-than-linear scalability... add more busses w/ more dirves...
more scalability... of course, not linear. Add caching effects, and
get superlinear scalabiltiy (but that doesn't count).

Your analysis is flawed because it assumes zero time
for disk-head seeks.


I do believe your the one who's full of s***.

I'm not the one making crazy statements that rely on
disk-heads using instant teleportation from track
to track.



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