dovecot - Oct 2011 - Indexes to MLC-SSD

Hi all,

is anyone on this list who dares/dared to store his index files on a 
MLC-SSD?

Regards,
Patrick

On 10/26/2011 4:13 PM, Patrick Westenberg wrote:
> Hi all,
> 
> is anyone on this list who dares/dared to store his index files on a
> MLC-SSD?
I have not.  But I can tell you that a 32GB Corsair MLC SSD in my
workstation died after 4 months of laughably light duty.  It had nothing
to do with cell life but low product quality.  This was my first foray
into SSD.  The RMA replacement is still kickin after 2 months,
thankfully.  I'm holding my breath...

Scanning the reviews on Newegg shows early MLC SSD failures across most
brands, early being a year or less.  Some models/sizes are worse than
others.  OCZ has a good reputation overall, but reviews show some of
their models to be grenades.

Thus, if you were to put indexes on SSD, you should strongly consider
using a mirrored pair.

-- 
Stan

On Mon, 2011-11-07 at 01:08 +0100, Patrick Westenberg
wrote:
> Ed W schrieb:
> 
> > See the "sticky" in my reply.  You use one of several
techniques to
> > ensure that users always end up on the server with the indexes on. 
That
> > way much of the IO is served from that local machine and you only
access
> > the SAN for the (in theory much less frequent) access to the mail
files
> > themselves.
> 
> I know you can afford that (IMAP) users always end up on one particular 
> server but afaik this only works for incoming IMAP connections.
> 
> My mail exchangers use dovecot-lda and I think indexes will be written 
> from these servers too or am I wrong with this?
You can use LMTP and LMTP proxying.

Timo Sirainen schrieb:
> On Mon, 2011-11-07 at 01:08 +0100, Patrick Westenberg wrote:
>>
>> My mail exchangers use dovecot-lda and I think indexes will be written
>> from these servers too or am I wrong with this?
>
> You can use LMTP and LMTP proxying.
I already use lmtp:unix:private/dovecot-lmtp as transport but where is 
the link to the indexes?

Jan-Frode Myklebust schrieb:
> Yes, and in ascii-art this becomes :-)
>
> MTA -(lmtp)-->  dovecot-director ---(lmtp)--->  backend-server1
>                                 \---(lmtp)--->  backend-server2
>
>
> IMAP-user  -(imap)-->  dovecot-director --(imap) -->  backend-server1
>                                        \--(imap) -->  backend-server2
I failed creating a nice ascii view ;-)

However, I have some more questions:

- What happens if the MTA accepted a message but the backend-server 
fails and is unable to store it?

- What about load-balancing and/or failover?
Maybe all users on backend-server1 are fetching their mails causing high 
load while backend-server2 is idle.
Is it possible to specify more than one backend-server IPs as I can do 
for the database hosts for userdb queries?

Jan-Frode Myklebust schrieb:
> MTA -(lmtp)-->  dovecot-director ---(lmtp)--->  backend-server1
>                                 \---(lmtp)--->  backend-server2
>
>
> IMAP-user  -(imap)-->  dovecot-director --(imap) -->  backend-server1
>                                        \--(imap) -->  backend-server2
In this scenario it should be possible to use a non cluster filesystem
to store my mails, isn't it?

Patrick