overview zlib efficiency?

[Andrew McGlashan]

On 16/03/2016 2:01 AM, Götz Reinicke - IT Koordinator wrote:
> Hi,
> 
> may be someone has already done that: Do you have a script(?) tool which
> shows the efficiency of the mail compression if zlib is used?
> 
> Something that shows the uncompressed size vrs. the compressed.

Remember one thing; emails are stored in plain text, the same text that
they are normally transmitted b/w servers.

With that in mind, text, particularly with repeating and common things
like headers (and other things), then you should get significant
reduction in size.

The exception of the size benefits (storage), is when you have emails
that are less than the file system block size (4k ext4 perhaps).  So
many emails are smaller than a block size and for those, zipping is not
much benefit as it won't make a scrap of difference to storage.
However, when you have users that send attachments and sometimes very
large attachments, well, it will save loads of storage on those emails.

Next, if you have a CPU bottleneck, then the extra overhead of
compression may also be an issue; but unless your server is working
hard, compression isn't likely to tax the CPU a great deal.

Cheers
Andrewm

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