Queue directories on faster media?

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Queue directories on faster media?

Ori Bani
Hello,

I'm curious to get feedback on the idea of mounting all the postfix
queue directories on a faster media (SSD drive in this case).

In my case, I have virtual maildirs under /var/spool/postfix and those
would be relocated to elsewhere (onto slower normal media) because the
faster (SSD) media isn't in a RAID configuration (slower media is).

Does that make any sense?  Is there adverse risk putting the queue
directories on non-RAID fast media?  Am I right to think that that's
where the most performance is to be gained?

I guess you could put some queue directories in tmpfs, but that seems
even more risky, a little too risky.
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Re: Queue directories on faster media?

Ralf Hildebrandt
* Ori Bani <[hidden email]>:
> Hello,
>
> I'm curious to get feedback on the idea of mounting all the postfix
> queue directories on a faster media (SSD drive in this case).
>
> In my case, I have virtual maildirs under /var/spool/postfix and those
> would be relocated to elsewhere (onto slower normal media) because the
> faster (SSD) media isn't in a RAID configuration (slower media is).

Why are you storing maildirs in the queue directory?
 
> Does that make any sense?  Is there adverse risk putting the queue
> directories on non-RAID fast media?  Am I right to think that that's
> where the most performance is to be gained?

Yep.

> I guess you could put some queue directories in tmpfs, but that seems
> even more risky, a little too risky.

--
Ralf Hildebrandt
  Geschäftsbereich IT | Abteilung Netzwerk
  Charité - Universitätsmedizin Berlin
  Campus Benjamin Franklin
  Hindenburgdamm 30 | D-12203 Berlin
  Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
  [hidden email] | http://www.charite.de
           
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Re: Queue directories on faster media?

Ori Bani
On Mon, Jan 30, 2012 at 12:42 AM, Ralf Hildebrandt
<[hidden email]> wrote:

> * Ori Bani <[hidden email]>:
>> Hello,
>>
>> I'm curious to get feedback on the idea of mounting all the postfix
>> queue directories on a faster media (SSD drive in this case).
>>
>> In my case, I have virtual maildirs under /var/spool/postfix and those
>> would be relocated to elsewhere (onto slower normal media) because the
>> faster (SSD) media isn't in a RAID configuration (slower media is).
>
> Why are you storing maildirs in the queue directory?

I think it is a legacy thing from a very old how-to.  Note it's for
virtual accounts, so no /home directories.  What's the more standard
place to put them if I may ask?

>> Does that make any sense?  Is there adverse risk putting the queue
>> directories on non-RAID fast media?  Am I right to think that that's
>> where the most performance is to be gained?
>
> Yep.

Thanks.  Would it be OK to put everything in /var/spool/postfix on
fast media or do only some directories benefit from the speed
increase?
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Re: Queue directories on faster media?

Stan Hoeppner
In reply to this post by Ori Bani
On 1/30/2012 1:47 AM, Ori Bani wrote:

> Does that make any sense?  Is there adverse risk putting the queue
> directories on non-RAID fast media?

SSDs, both MLC and SLC, do fail, just not the same failure modes as
SRDs.  Thus you need to use a mirrored pair for the Postfix spool, just
as you'd do with spinning rust discs.

I've owned a total of 1 SSD, an MLC consumer Corsair model.  It failed
after 3 months.  The replacement has lasted longer (knocks on wood).
Not used in a server role but a desktop.  Failed due to poor QC, not
write load.

--
Stan
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Re: Queue directories on faster media?

/dev/rob0
In reply to this post by Ori Bani
On Mon, Jan 30, 2012 at 01:09:29AM -0800, Ori Bani wrote:

> On Mon, Jan 30, 2012 at 12:42 AM, Ralf Hildebrandt
> <[hidden email]> wrote:
> > * Ori Bani <[hidden email]>:
> >> I'm curious to get feedback on the idea of mounting all the
> >> postfix queue directories on a faster media (SSD drive in
> >> this case).
> >>
> >> In my case, I have virtual maildirs under /var/spool/postfix
> >> and those would be relocated to elsewhere (onto slower normal
> >> media) because the faster (SSD) media isn't in a RAID
> >> configuration (slower media is).
> >
> > Why are you storing maildirs in the queue directory?
>
> I think it is a legacy thing from a very old how-to.

Having recently written a Postfix howto, I reviewed quite a few
others in the process. With few exceptions I found that they were
written by people with a poor understanding of Postfix. This was
especially true of the old, unmaintained howto documents.

> Note it's for virtual accounts, so no /home directories.

A virtual user should have a $HOME, but perhaps that is not what
you're talking about. In my own system I happen to use
        virtual_mailbox_base = /home
because that filesystem has the most room for storage.

> What's the more standard place to put them if I may ask?

There is no standard, as shown by the default postconf(5) value of
$virtual_mailbox_base. However there is the official Postfix
VIRTUAL_README.html#virtual_mailbox document, which uses this:
        virtual_mailbox_base = /var/mail/vhosts

As hinted above, I suggest sticking with the official Postfix
documentation. Look at third-party howtos for ideas, but you
shouldn't rely on them for exact guidance. When their ideas don't
mesh with what is in Postfix documentation, consider the entire
document to be of dubious quality.

> >> Does that make any sense? Is there adverse risk putting the
> >> queue directories on non-RAID fast media? Am I right to think
> >> that that's where the most performance is to be gained?
> >
> > Yep.
>
> Thanks.  Would it be OK to put everything in /var/spool/postfix
> on fast media or do only some directories benefit from the
> speed increase?

I wouldn't think it worth the trouble to try to separate actual
queues from the few other files under /var/spool/postfix/. But then,
I am not sure that there is an actual problem that this idea will
solve. :)

We here tend to want to focus on real problems. If everything is
working well, don't tinker. Postfix default settings generally are
good; a competently-managed system's "postconf -n" should typically
be very short.
--
  http://rob0.nodns4.us/ -- system administration and consulting
  Offlist GMX mail is seen only if "/dev/rob0" is in the Subject:
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Re: Queue directories on faster media?

Simon Brereton-2
On 30 January 2012 12:49, /dev/rob0 <[hidden email]> wrote:

> On Mon, Jan 30, 2012 at 01:09:29AM -0800, Ori Bani wrote:
>> On Mon, Jan 30, 2012 at 12:42 AM, Ralf Hildebrandt
>> <[hidden email]> wrote:
>> > * Ori Bani <[hidden email]>:
>> >> I'm curious to get feedback on the idea of mounting all the
>> >> postfix queue directories on a faster media (SSD drive in
>> >> this case).
>> >>
>> >> In my case, I have virtual maildirs under /var/spool/postfix
>> >> and those would be relocated to elsewhere (onto slower normal
>> >> media) because the faster (SSD) media isn't in a RAID
>> >> configuration (slower media is).
>> >
>> > Why are you storing maildirs in the queue directory?
>>
>> I think it is a legacy thing from a very old how-to.
>
> Having recently written a Postfix howto, I reviewed quite a few

URL please? :)

Simon
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Re: Queue directories on faster media?

Viktor Dukhovni
In reply to this post by Ori Bani
On Sun, Jan 29, 2012 at 11:47:39PM -0800, Ori Bani wrote:

> I'm curious to get feedback on the idea of mounting all the postfix
> queue directories on a faster media (SSD drive in this case).

The answer depends on your real goals. Mounting the spool on an
SSD is only your real goal if you're are a compulsive tinkerer.
Otherwise, you're trying to solve some problem that's motivating
this question, so state that instead.

> In my case, I have virtual maildirs under /var/spool/postfix

This is a bad idea. The /var/spool/postfix directory is just for
the Postfix queue (messages in transit). Do not deliver mail there.
Ideally deliver mail into a separate file-system that does not
compete for space with the Postfix queue.

> Does that make any sense?  

Not without a reason to consider SSD. Do however avoid using
/var/spool/postfix for user maildirs, that's a mistake.

--
        Viktor.
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Re: Queue directories on faster media?

Ori Bani
On Mon, Jan 30, 2012 at 10:27 AM, Viktor Dukhovni
<[hidden email]> wrote:
> On Sun, Jan 29, 2012 at 11:47:39PM -0800, Ori Bani wrote:
>
>> I'm curious to get feedback on the idea of mounting all the postfix
>> queue directories on a faster media (SSD drive in this case).
>
> The answer depends on your real goals. Mounting the spool on an
> SSD is only your real goal if you're are a compulsive tinkerer.

Haha.  :)

> Otherwise, you're trying to solve some problem that's motivating
> this question, so state that instead.

No, no problem.  Only attempting to future-proof things.  I anticipate
mail volume to grow in the future, and as I have access to SSD, I
thought maybe postfix would run faster using it under its queues.  Is
this not the case?

>> In my case, I have virtual maildirs under /var/spool/postfix
>
> This is a bad idea. The /var/spool/postfix directory is just for
> the Postfix queue (messages in transit). Do not deliver mail there.
> Ideally deliver mail into a separate file-system that does not
> compete for space with the Postfix queue.

Point taken, glad I accidentally bumped into this advice.
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Re: Queue directories on faster media?

Viktor Dukhovni
On Mon, Jan 30, 2012 at 12:00:08PM -0800, Ori Bani wrote:

> > Otherwise, you're trying to solve some problem that's motivating
> > this question, so state that instead.
>
> No, no problem.  Only attempting to future-proof things.  I anticipate
> mail volume to grow in the future, and as I have access to SSD, I
> thought maybe postfix would run faster using it under its queues.  Is
> this not the case?

Generally, there is no performance advantage, unless the disk is
a significant bottleneck for your workload. If you're receiving
mail, generally the bottleneck is content inspection.

If you're sending mail at under 100 msgs/sec, or virus-scanning
outbound mail, a modern server with a RAID controller with a BBU,
will be plenty fast. If you to get well north of ~300 msgs/sec,
then perhaps you need a faster disk, or more machines, whichever
is more cost effective.

For a sufficiently expensive SSD, another server may be a better
option, though cost of cooling, power and data-center space also
comes into the equation.

--
        Viktor.
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Re: Queue directories on faster media?

Ralf Hildebrandt
In reply to this post by Ori Bani
> > Why are you storing maildirs in the queue directory?
>
> I think it is a legacy thing from a very old how-to.  Note it's for
> virtual accounts, so no /home directories.  What's the more standard
> place to put them if I may ask?

Anywhere else, like /var/spool/mail (just an idea)

> Thanks.  Would it be OK to put everything in /var/spool/postfix on
> fast media or do only some directories benefit from the speed
> increase?

I would put ONLY the WHOLE queue directory there.

--
Ralf Hildebrandt
  Geschäftsbereich IT | Abteilung Netzwerk
  Charité - Universitätsmedizin Berlin
  Campus Benjamin Franklin
  Hindenburgdamm 30 | D-12203 Berlin
  Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
  [hidden email] | http://www.charite.de