Veritas-bu

[Veritas-bu] iostat during duplication - strange

2002-04-04 09:29:58
Subject: [Veritas-bu] iostat during duplication - strange
From: kk_downings AT yahoo DOT com (kk downing)
Date: Thu, 4 Apr 2002 06:29:58 -0800 (PST)
So the Multiplexing factor dictates how many different
client's blocks might exists within a fragment? Is
that correct?

Thanks
kk
--- "Urbanec, Peter" <peter.urbanec AT csfb DOT com> wrote:
> > I am demultiplexing during duplication
> 
> Yup! It looks like your MPX factor is 2 and so you
> throw away about
> half the data you read.
> 
> > I thought that multiplexed backups were interwoven
> fragments.
> 
> Nope, the data is multiplexed within the data stream
> at the block level
> and each block has a header that identifies to which
> stream it belongs.
> 
> > Shouldn't I be reading one image's fragment,
> skipping over another,
> > then reading another appropriate fragment?  (you
> know: "mt fsf #")
> 
> Nope. You would require quite a lot of buffering to
> make this workable.
> 
> > Your comments suggest that data within fragments
> is from
> > multiple clients? 
> 
> That's how it works. See page 644 of the UNIX Admin
> Guide.
> 
> > If this is the case, I may have the answer to my
> slow
> > duplications
> 
> Yes and no. It will slow you down, but only by the
> level of
> multiplexing. Some of us are seeing much worse
> performance
> problems and are preserving the multiplexing.
> 
> My vaults will go down to 50KB/s for some random
> parts :-(
> 
> 
>         Peter Urbanec    B.Sc.(Comp.Sci.)  UNSW
>         mailto:peter.urbanec AT csfb DOT com
> 
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