Cyrus-imapd memory tuning

[Bron Gondwana]

On Wed, Mar 12, 2014, at 08:11 PM, Marco wrote:
> > On Mon, Mar 10, 2014, at 07:49 PM, Marco wrote:
> >> With 8GB RAM,
> >
> > I would recommend you increase that...
> [...]
> > As an interesting datapoint, the big ones cost about US$20k fully  
> > stocked, including 40Tb of RAID6 storage for email, plus 6Tb of  
> > RAID1 for search indexes and 800Gb of RAID1 SSD for hot metadata.
> [...]
> 
> Hello,
> 
>    with these servers could you tell me what is the average number of  
> IMAP processes (connections) opened? Just for understand a real  
> example relationship between memory and processes.

Looks like on a medium-loaded server we have about 15,000 connections open
at the moment.  It's about 40% masters, 40% replicas, 20% unallocated.

> About disk, what is the high size of a single partition managed by Cyrus?

We're just using a single partition (default) in each instance of Cyrus,
but there are multiple instances installed.

The config is somewhat complex, we're running a patch which enables 'archive'
storage.  It's a little bit buggy still, but good enough for our purposes
with some babysitting.

The 'spool' path is on a shared SSD (400Gb x RAID1), but there's a separate
archive partition for each slot with 1Tb of space allocated.

So overall it's laid out as two x 12 drive RAID6 of 2Tb drives, each with a
20Tb volume which is them configured with GPT partition table as 20 separate
1Tb partitions.

There's also a separate 3-drive RAID 1e (3Tb storage striped over 3 disks)
with search data, using yet another set of patches which integrate the Xapian
search engine into our Cyrus system for fast full-text searches.

I've nearly finished writing a blog post which incidentally glances over some
of this stuff while talking about a recent outage.

Bron.

-- 
  Bron Gondwana
  brong at fastmail.fm