[Dovecot] dovecot evaluation on a 30 gb mailbox

[Rajesh M]

> Timo Sirainen put forth on 6/19/2010 9:43 PM:
>> On 20.6.2010, at 3.33, Rajesh M wrote:
>>
>>> 3) next i changed squirrelmail display preference to list 500 mails per
>>> page
>>> and then clicked on inbox ... expecting dovecot to take atleast around
>>> 1-2
>>> mins to show the mails
>>>
>>> ... the mails were displayed in just 8 seconds .. awesome performance
>>
>> Fetching metadata for 500 messages took 8 seconds? Still sounds slow.
>> Although maybe it's because of maildir. I'm anyway not happy until
>> Dovecot can open a mailbox with millions of messages and access them in
>> nearly constant time (few milliseconds, with SSD).
>
> Roundcube 0.3.1 seems to have a hard coded limit of 200 mails per page.
> On a
> dual CPU 500 MHz Celeron with 384MB and a single 500GB SATA drive, running
> both RC and Dovecot 1.2.11 on the box, it takes about 5 seconds to pull
> metadata for each set of 200 messages on a 13k+ message mailbox.  This is
> using mbox.
>
> I agree with Timo, 8 seconds for 500 messages on that hardware seems a bit
> slow given what my lowly setup can do.  Was the box under load when you
> tested
> or idle?  What disk subsystem is the maildir stored on?  Single disk or
> high
> performance RAID?  Was the disk subsystem under load or idle when you
> tested?
>
> --
> Stan
>


stan

my machine is dual core dual processor xeon 1.6 gig proc
4 gb ram
1 tb sata for centos linux
1 tb sata for vpopmail domains data, mysql db and log data
my hdd usage is at 60 percent now.

i accessed the large email box (this is qmail tap account in which emails
are continuously added) yesterday 10 pm at night
login took around 5 mins
Around 169000 emails in the box

I logged out and logged in again after around 5 mins -- access took just
around 4-5 seconds. Around 10 emails had been added.

at 10 am in the morning today i logged in again ie around 12 hours after
above login.

it again took around 4-5 mins

i have currently over 170000 emails in the mailbox ie overnight around
1000 emails were added
i logged off and access again -- the mailbox opened in around 5 seconds

so what i can conclude is that if relogin after a few minutes then the
access is very fast whereas if i do the same after a few hours then it
takes time.

i am new to dovecot and a few questions

1) is it ok that dovecot takes 5 mins every time i login if there is
significant time difference between the two logins

2) as per what timo said the metadata is cached so the data pertaining to
the extra 1000 emails were to be added to the cache .. does dovecot go
thru all the 170000 emails again to form the meta data ? or is there some
cache expiry period ?

thanks
rajesh