Re: How to calculate a useful size for a given pool

From: Brian Evans (b..evans_at_sympatico.ca)
Date: 08/02/04 

Date: Mon, 2 Aug 2004 15:44:27 -0400

"Gareth Williams" <gareth@nospam.com> wrote in message
news:pan.2004.08.02.11.50.20.547414@nospam.com...
> Scenario:
>
> 1. A firm receives 100,000 orders per week as electronic documents.
>
> 2. All documents are archived on CDROM.
>
> 3. A percentage of orders (average around 10%) will go wrong at some
> stage and access to the original order will be required by Customer
> Services to resolve the problem.
>
> 4. Retrieval from CDROM is time-consuming but a limited amount of space is
> available to cache some of the documents on networked storage for more
> immediate retrieval. There is not enough space to cache all the documents
> so the older cached documents are deleted regularly.
>
> 5. It is not possible to determine "up front" which orders will fail -
> whilst the failure rate is fairly constant over time, just about any
> document could end up being requested by Customer Services.
>
> Problem:
>
> The firm would like to cache "N" documents (from the weekly pool of
> 100,000 orders) such that they can satisfy "X" percent of Customer Service
> requests from the networked storage. Customer Services are prepared to
> put up with [100-X]% of requests that would still need to be retrieved
> from the CDROM store.
>
> In short, how do we calculate "N"?
>
> This reminds me a little of the "Cookie Jar" or "Sock Drawer" problem,
> but it bugs me that I can't puzzle it out. I'm not a hard-core
> statistician and would be grateful for any help. This is a genuine (i.e.
> non-homework) request, by the way. I've posted to other NGs with no luck
> so far.

#4 mostly likely doesn't hold true anymore.
Hardrives have increased in capacity making caching all the data easy. A
single 250gb drive caches 384 CDs worth at 650mb per CD. A fully
decked out $10,999 Apple XServe RAID would cache 5384 CDs.
Thats 35/mb of electronic documents per order if 100,000 are
stored on the XServer at any one time.

Relevant Pages

  • Re: How many documents to store?
    ... Gareth Williams writes: ... All documents are archived on CDROM. ... > document could end up being requested by Customer Services. ... Suppose the fraction of documents you cache is p = N/50000. ...
    (sci.math.num-analysis)
  • How to calculate a useful size for a given pool
    ... A firm receives 100,000 orders per week as electronic documents. ... All documents are archived on CDROM. ... document could end up being requested by Customer Services. ... requests from the networked storage. ...
    (sci.math)
  • Need an equation to work out file cacheing
    ... A firm receives 100,000 orders per week as electronic documents. ... All documents are archived on CDROM. ... document could end up being requested by Customer Services. ... requests from the networked storage. ...
    (sci.stat.math)
  • How many documents to store?
    ... All documents are archived on CDROM. ... document could end up being requested by Customer Services. ... networked storage. ... We are prepared to put up with % of requests ...
    (sci.math.num-analysis)
  • Re: Need an equation to work out file cacheing
    ... As a real-world problem -- Are you referring to huge .pdf scans ... I'm curious - really, CDROM, for high-capacity backups? ... There is not enough space to cache all the documents ... > document could end up being requested by Customer Services. ...
    (sci.stat.math)