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Date: Thu, 18 Dec 2008 10:09:42 -0800
From: Andrew Sharp <andy.sharp@onstor.com>
To: Neil Cook <neilc@onstor.com>
Cc: "Michael Tracy (Glasshouse)" <mtracy@css.glasshouse.com>, dl-cstech
 <dl-cstech@onstor.com>, Edwin Rodriguez <erodriguez@css.glasshouse.com>
Subject: Re: Cougar performance - external copy vs internal copy
Message-ID: <20081218100942.281d6ea7@ripper.onstor.net>
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I would liken this to copying a file from one disk to another disk
versus copying the file to another file on the same disk.  The former
will be faster because the I/Os can overlap more.  It's the basic "more
spindles" principle.

Cheers,

a


On Thu, 18 Dec 2008 06:12:39 -0800 Neil Cook <neilc@onstor.com> wrote:

> Mike,
> 
> From this I'd suggest that the reason for the delay is because the
> copy isn't 'internal' as suggested. The first copy will has three
> stages, source-client-target, where as the second copy only has two
> stages, source and target. Therefore the reason the differing speeds
> is that the first copy has to go across the network twice, once to
> the client and then from the client to the target.
> 
> 
> Regards,
> 
> 
> [cid:image001.jpg@01C9611A.7EDA00B0]<http://www.onstor.com/>
> Neil Cook
> Senior Technical Support &
> Escalations Engineer
> 
> ONStor, Inc.
> Email: Neil.Cook@ONStor.com
> Web:   http://www.ONStor.com
> 
> EMEA Support Line
> Phone:   +44 (0) 8707 347 448
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> Web:     http://Support.ONStor.com
> 
> ________________________________
> From: Michael Tracy (Glasshouse)
> Sent: 18 December 2008 13:17
> To: dl-cstech
> Cc: Edwin Rodriguez
> Subject: Cougar performance - external copy vs internal copy
> 
> Hi all
> Customer noticing a difference of speed from an external copy to an
> internal copy.
> 
> We tried copying a 3Gb folder from one location to another on the
> same volume while the vsvr was on cougar. The copy took 6 minutes.
> When we take the same 3Gb folder and copy it from a Windows server to
> a vsvr on cougar, it takes 4 minutes. This copy is a single thread
> from a single server.
> 
> My thoughts are this is due to an internal copy putting more load on
> the back end (read and write) while an external copy does less
> (write) That said, are there any suggestions to improve this copy
> time? Other than the TOI ppt, I haven't been able to find performance
> info. What kind of performance numbers should we expect?
> 
> Michael
