Network Client-Cache

by Johannes Helmig [Published on 1 May 1998 / Last Updated on 1 May 1998]

When it come to network-speed/through-put, there is one fact:
It is NEVER fast enough, users want more speed !

Lets have a look at the components of a network:

Typical bandwidth / through-puts:
- network-cable: 0.5 - 2 MByte/sec
- Server to Disk-cache: ~ 20 MByte/sec
- Disk-cache <-> Disk: 2-5 Mbyte/sec

Servers keep the most common used data in their disk-cache, in such cases the limiting factor is usual the band-width of the network cable.

To get more speed into the network, some network-client (like: Novell Client32, Sun Solstice NFS Client) offer now an integrated local cache:

If any data has been previously used by the
Client, it can be found in the local
of the Client, which can be
accessed MUCH faster (~20 MByte/sec)
compared getting it it via the network
(Typical through-put: 0.5 - 2 Mbyte/sec
plus delays due to server-response time,
which becomes an issue on busy servers).

That is fine, if the client is the ONLY system accessing the files.
But when multiple Clients access the same data:

There are now 3 locations,
where the data is stored:
- the Cache/disk of the Server
- the Net-Cache of Client#1
- the Net-Cache of Client#2

The designers of these Network-Clients with integrated local Cache do their best to ensure synchronization, however experience has shown, that this is NOT always successful, especially when using database-programs ( when multiple client modify SIMULTANEOUSLY the same data-file):
If the synchronization fails, the data-files are getting corrupted !

In such cases, turn-off/de-activate the Net-Cache, because:
Stability and Data-Integrity are more important than Network-Speed !

There is a possibility, that the Microsoft Network Client can corrupt data files in certain conditions, for details see: Possible Data Corruption by Microsoft Network Client

See Also

The Author — Johannes Helmig

Dr.Johannes Helmig is working as Director, Technical Knowledge Management in the Belgium office of Gerber Technology where he is involved in Customer Service and internal training, with special interest in Networking.


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