[Zope] Re: WHY ? -- Performace in serving large media filesfrom ZODB vs from external file system

[Sedat Yilmazer]

 Hi Zopers
=20

 In most of the systems  ( specially where we have a server and =
performanace requirements) we have high end systems with fast disk =
access. In such system the problem most of the time is the CPU =
power/RAM/Internet Connection Speeds. If you have a system with a =
2-8Mbps your basic bottleneck is at the CPU and RAM side, NOT at the =
Disc IO side.


 Lets assume that the total response time is=20

 setting up the client/server connection + (How is it in ZServer forks? =
)=20
 request processing + =20
 finding the object in ZODB +=20
 Reading the object from ZODB +=20
 writing the data to temp file +=20
 pushing the file to client

 In this picture writting the file once more to the file system should =
not be a big part of the picture. In most systems IO is initiated by the =
CPU and completed by the hardware (DMA). If your channel to HD can not =
cope with that you must have the fastest Internet connection on the =
plannet.


 So as the last point. I would never ever giveup a consistent =
implementation if the performance inrease is  less then %100.
 HW is so cheap that spending some days to get thing working may cost =
you alot more.=20

 Sedat

=20

-----Original Message-----
From: zope-admin@zope.org [mailto:zope-admin@zope.org]On Behalf Of
Dieter Maurer
Sent: Saturday, July 07, 2001 11:32 AM
To: marc lindahl
Cc: zope@zope.org
Subject: Re: [Zope] Re: WHY ? -- Performace in serving large media
filesfrom ZODB vs from external file system


marc lindahl writes:
 > > From: Dieter Maurer <dieter@handshake.de>
 > > I have to admit that I did not make any measurements.
 >=20
 > This is what we need, some real world numbers.
Go ahead!
 > ...
 > I wonder why this temp file is used....  but just because a file is =
used
 > doesn't make it twice as slow.  Either the whole system needs to be =
analyzed
 > or measured.
Sure, but it may well do, if you have a really fast network or
access it locally.

  The most efficient solution: read file in chunks and stream it onto
  the TCP connection.

  ZServer's solution: read the file in chunks, write to a temporary
  file. Read the temporary file in chunks and stream it
  onto the TCP connection.
  Additional overhead: Reading and writing the file once.


Dieter

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