HCN email is a nice response but it is assuming we use the University or
other caching systems for e-journals and database access which we don't
1. All searches are unique and therefore would not have use of
returning previously cached pages from a caching system as a results page,
so would therefore return a result from HCN not the cache. Anyhow, once you
refresh you should get a live page.
2. Our e-journals access in which we download PDF's also does not use a
proxy cache due to IP masking, so when we download a PDF from a journal site
it is directly from the publishers server and NOT a cached one at MCC or
other NHS cache
So the user Can tell where their PDF file is coming from
Regards
Steve
-----Original Message-----
From: [log in to unmask]
[mailto:[log in to unmask]]
Sent: 23 October 2001 11:20
To: [log in to unmask]
Subject: ADITUS performance issues
Hello
I have been discussing the issues of bandwidth and speed of
access with HCN. Although I have not been following the discussion in
detail, I have been concerned that some of the discussion has been
inaccurate. I have been very blunt with HCN asking them if their servers are
slow and causing some speed of access problems in the north west. I have
also asked the Managing Director if HCN is 'fobbing off' the north west as
one email suggested.
I intend to work via the LIS Patch Groups in those areas
were speed is clearly an issue. In the meantime, below is an email from HCN.
Regards
Colin
Please email me direct @ [log in to unmask]
<mailto:[log in to unmask]>
COLIN DAVIES.
Deputy Director of Health Libraries - Information
Technology.
Northwest Health Care Libraries Unit.
Thelwall House
Lovely Lane
Warrington
WA1 1QG
-----Original Message-----
From: p=NHS NATIONAL
INT;a=NHS;c=GB;dda:RFC-822=robin.turner(a)hcn.org.uk;
Sent: 22 October 2001 19:37
To: Davies, Colin
Cc: p=NHS NATIONAL
INT;a=NHS;c=GB;dda:RFC-822=allison.hartman(a)hcn.com.au;
Subject: performance issues
Colin
I have looked again at the situation with regard to the
apparent speed discrepancies being reported from the North West Region.
Our original starting point was that a significant number of
users have always reported a good reponse, Your message seems to confirm
this, thus verifying that for them at least, the servers are delivering a
good 'turn round', you site 5 seconds as a response below.
What puzzled us was that some individuals reported
perfomance results of much longer times, 1 hour. This leads to the
conclusion that since all users access the same servers it logically has to
be something that effects some users locally. It can't be the servers, or
our link bandwidths, or ALL users in ALL areas would be similarly effected,
which is not the case.
Also some of those times reported are difficult to accept,
the intermediate server 'times out' well within the time limit and no
response would be passed. Our original suspicion of interconnect bandwidth
does hold true for some local NHSnet connections with bandwidth limitations,
but not all. Only those who have a degraded response but probably only
within a minute or so.
Investigations recently have led to an interesting
development. We believe that in some locations network trafic is cached.
This WILL cause a problem since the WebSpirs pages are dynamic and hold
session data that is time specific. If a cacheing server intercepts and
responds instead of the HCN servers this will interfere with the process and
the response will be unpredictable. Our system manager has asked the
manchester cachemaster to exclude us from the process which if properly
performed, will I firmly believe alleviate the situation.
Interestingly, cacheing is normally in place to improve the
response times of networks when there is limited bandwidth which needs to be
conserved, and the same pages are being repeatedly accessed. The Manchester
cachemasters assertion that there is more than adequate bandwidth seems to
contradict the need for cacheing in the first place. A curious paradox.
Also users with a 'stalled' screen get an almost instant
response when they hit the F5 key to refresh the screen.
FYI The HCN server configuration is set up so that a dynamic
web front end session is run on one set of servers (WebSpirs) to collect the
searches which are then passed internally to a database back end (ERL). This
back end responds to the internal server over a fast ethernet link which
then wraps the answer and presents it back.
The ERL database server is well over specified for the
actual load. The response from the Webspirs servers is fairly constant
inasmuch that we don't seem to see adverse comments in terms of logging in
or displaying the search entry screens, only the database searches.
Internally we test our own service by using a 64k line from
Demon to get out to the internet and then back through the bigger link from
UUnet to simulate the performance available to customers.
To check, I have just tried a search to Embase resulting in
9994 hits which took 4 seconds to display and 3 to begin to show the
results. The more complex search 'calcium and antagonist and unstable and
angina' took 6 seconds to search. Not especially slow.
The way to demonstrate is to get the librarians to try it
from home via the internet on their own machines and dial up connections.
The comment below in your quote would actually bear out the
Cache theory since the download of the PDF file might actually not be coming
across the net at all, but from local cache. The user cannot tell ! And
having a big connection is a bit like the M6 southbound just north of
Birmingham on a wet friday evening, sure it's big - but is it quick ?
Finally, and perhaps most importantly, I would never 'fob
off' a customer.
HCN is rightly proud of it's service.
Happy to keep up investigating till we eventually find the
bottleneck !!!
Robin Turner
Head of Information Systems
HCN
Charwell House Alton
Hampshire GU34 2PP
Tel: +44 (0) 870 8723 003
Fax: +44 (0) 870 8723 004
E-mail: mailto:[log in to unmask]
<mailto:[log in to unmask]>
Web: www.hcn.org.uk <http://www.hcn.org.uk>
'The Leader in Health Internet & Clinical Software'
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