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From Jan Lehnardt <...@apache.org>
Subject Re: [user] Couch as a mail store?
Date Thu, 12 Feb 2009 14:59:01 GMT

On 12 Feb 2009, at 15:50, Wout Mertens wrote:

> On Feb 12, 2009, at 3:13 PM, Kenneth Kalmer wrote:
>
>> Normal filesystem-based storage of mail has other issues:
>>
>> * Messages often smaller than ethernet jumbo frames, so limited  
>> throughput
>> (couch can overcome this by bundling messages in a single response)
>
> wow that's really specialized. Is that really an issue?
>
>> * Mostly limited by disk IO and clever tricks around solid state  
>> drive usage
>> or stripping excessively fast disks
>
> Hmmm makes me wonder - CouchDB doesn't change the position of  
> received documents on disk, so retrieving a view could mean many  
> disk accesses.
>
> Is that correct? Is that something all databases suffer from? I  
> suppose the only answer for that is caching?

The file and b-tree structure is actually made to require a minimal
number of disk head seeks (which is what makes disks slow) and
in a typical usage scenario, upper nodes of the btree are cached
in the filesystem buffer cache too, so there's another speedup.

Cheers
Jan
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