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
Net-Cache
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

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