overview zlib efficiency?

[Rick Romero]

  Quoting Robert L Mathews <lists at tigertech.com>:

> On 3/15/16 10:13 AM, Sven Hartge wrote:
>
>> I don't have a script, but I can provide some numbers. I did a test with
>> a server for about 10.000 users and 2TB worth of mail, converting from
>> Maildir++ to mdbox with zlib (level = 6) and had a final size of 1TB, so
>> 2:1 reduction.
>
> These numbers roughly match my results. About 6 TB of mail compresses
> down to about 3 TB.
>
> Also keep in mind that even if it does increase CPU usage, it reduces
> disk usage. This is probably an excellent tradeoff for most people,
> since most servers are limited by disk throughput/latency more than CPU
> power.

Just thought I'd add, because it frustrated me and it's an amusing anecdote
to this - The new 4k ashift doubled my disk usage of Maildir++ mail.

So logically, if you're migrating from maildir++ to mdbox on 4k sector
system, you may see a sizable decrease in disk usage without a compression
change.

Rick