Re: Adding archiving to an existing Cyrus installation

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On Fri, 10 Nov 2017, at 00:02, Nic Bernstein wrote:
Bron,
Thanks for the response.  Your solution has pointed us towards the proper approach.  We are using ZFS, so would be performing ZFS send/receive replication rather than "mv", to move the filesystems.  Our typical approach for this sort of thing, then, would be:


That's basically exactly how FastMail's user moves work, and the sync-protocol based XFER that Ken built based on it.  Except inside Cyrus rather than at the FS level.

To quiesce the filesystem, we would normally like to tell whatever applications are using it to temporarily freeze operations, so the underlying filesystem is in a consistent state.  When I was in Melbourne, back in April, we (you, Ellie & I) discussed what would be needed to introduce such a feature to Cyrus.  I'm curious if there's been any further discussion or work on this?  Should I open a feature request?

There has been discussion, not yet work.

https://github.com/cyrusimap/cyrus-imapd/issues/1763

It would be nice to be able to complete consistent snapshots for filesystem operations like replication or backup, and this is a feature of many large applications, such as mail and DB servers.

Yep :)  It's on our radar.  There's a whole lot of work planned - Ken is going to write up the notes on that at some point.  We had a planning meeting while he was in Australia.

Thanks again for shining a welcome light on how to achieve the goal of adding archive to an existing system.

Cheers,
    -nic


On 11/04/2017 10:59 PM, Bron Gondwana wrote:
Hi Nic,

Sorry I didn't get back to answering you on this the other day!

So... this one is kinda tricky, because everything is going to be on "spool", but here's how I would do it.

Before:

/mnt/smalldisk/conf -> meta files only
/mnt/bigdisk/spool -> all email right now

Stage 1: splitting:

/mnt/smalldisk/conf
/mnt/bigdisk/spool
/mnt/bigdisk/spool-archive -> empty

And set archivepartition-default to /mnt/bigdisk/spoolarchive

Now you need to run an initial cyr_expire.  This will take a long time, but it should be able to use hardlinks to move the files - it's using cyrus_copyfile.

Once cyr_expire has finished an most of your email is moved into spool-archive, shut down cyrus.

mv /mnt/bigdisk/spool /mnt/smalldisk/spool

And set partition-default to /mnt/smalldisk/spool

That way your downtime is only while the small remaining spool gets moved to the other disk.

Bron.


On Sun, 5 Nov 2017, at 02:58, Nic Bernstein wrote:
Thanks much to you  both for your comments and suggestions.  We had
already considered creating a temporary "staging" partition and
shuffling mailboxes around, as Michael discussed, but have the same
reservations about it.  Since we're dealing with nearly 6TB of data,
most of it old, this scheme would introduce considerable disruption to a
very active mail system.  We have a hard time getting a two hour
maintenance window, and this would take days!

Bron, other Fastmailers, any thoughts??
    -nic

On 11/03/2017 11:20 AM, Michael Menge wrote:
Hi,

Quoting Reinaldo Gil Lima de Carvalho <reinaldoc@xxxxxxxxx>:

I think that singleinstancestore (message hard links) will not
survive when
moving from one partition to the other and storage total size will
increase
significantly.


thanks for the hint. This was not a problem while migration to the
meta-data partition,
as the mails stayed on the same partition (as in file-system and not
cyrus-partition)
and only hardlinks where change at all.

So one more reason for an other migration path.



2017-11-03 12:22 GMT-03:00 Michael Menge
:

Hi Nic,

Quoting Nic Bernstein <nic@xxxxxxxxxxx>:

Friends,
I have a client with Cyrus 2.5.10 installed.  Last year we migrated
their
old 2.3.18 system to 2.5.10, with an eye towards an eventual move to
3.0.x.  Based on Bron's most excellent email of last year,
([Subject: Cyrus
database and file usage data] from Cyrus Devel of 8 January 2016)
we used a
tiered layout for the storage:

The main categories are:

 * Config directory (ssd) [/var/lib/imap]
     o sieve
     o seen
     o sub
     o quota
     o mailboxes.db
     o annotations.db
 * Ephemeral [/var/run/cyrus -- in tmpfs]
     o tls_sessions.db
     o deliver.db
     o statuscache.db
     o proc (directory)
     o lock (directory)
 * Mailbox data [typical 2.5.X usage]
     o Meta-data (ssd)
         + header
         + index
         + cache
         + expunge
         + squat (search index)
         + annotations
     o Spool data (disk: raidX)
         + messages (rfc822 blobs)

We sized the Fast SSD pool (this is three-drive mirrors on ZFS) to be
extra large, so it could eventually handle "Hot" data, and left
about 300GB
free there.  Data, on spinning media, is currently 5.74TB with
4.8TB free
(RAID10).  Metadata is 35GB and /var/lib/imap is 8GB, all of which
is in
the Fast pool.

Now the client is ready to take the dive into v3.0, and I'm trying to
figure out how to put "archive" operation in effect.

I have read the documentation (hell, I wrote most of it) and
understand
the settings, but what I cannot quite wrap my brain around is this:
There
is already all of this data sitting in all of these data partitions
(we use
a total of 34 separate partitions each for data & metadata) so how
do I
make the transition to separate archive partitions, since all that
data is
on the "slow" drives? Can I just reassign all of the current data
partitions to archivedata partitions, define the new set of "Hot" data
partitions on the Fast pool, and let 'er rip, or what?

I promise, if you tell me, I'll write it up as real documentation. :-)


We are interested in such a migration too. Our fallback plan, if we
don't
find a
better way to do it is, do use the same method as we introduced the ssd
meta-data
partition.


1. We created a new partition in our cyrus configuration,
2. we moved moved the accounts from one partition to the other one
by one.
3. (this will be new for the archive partition) run cyrus expire to
move
the old mails back to the slow disks.

This method will have two downsides.
1. we have to copy all mails to the fast storage, and move the old
mails
   back to the slow storage. So we have to move most of the mails
twice.
2. the path of the old mail will change so they will be stored again in
   our file based backup

so a method without these downsides will be appreciated

Regards

   Michael

------------------------------------------------------------
--------------------
M.Menge                                Tel.: (49) 7071/29-70316
Universität Tübingen                   Fax.: (49) 7071/29-5912
Zentrum für Datenverarbeitung          mail:
Wächterstraße 76
72074 Tübingen

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M.Menge                                Tel.: (49) 7071/29-70316
Universität Tübingen                   Fax.: (49) 7071/29-5912
Zentrum für Datenverarbeitung          mail:
Wächterstraße 76
72074 Tübingen

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Nic Bernstein                             nic@xxxxxxxxxxx
Onlight Inc.                              www.onlight.com
6525 W Bluemound Rd., Ste 24              v. 414.272.4477
Milwaukee, Wisconsin  53213-4073          f. 414.290.0335

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--
  Bron Gondwana, CEO, FastMail Pty Ltd
  brong@xxxxxxxxxxxxxxxx




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-- 
Nic Bernstein                             nic@xxxxxxxxxxx
Onlight Inc.                              www.onlight.com
6525 W Bluemound Rd., Ste 24	          v. 414.272.4477
Milwaukee, Wisconsin  53213-4073	  f. 414.290.0335

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  Bron Gondwana, CEO, FastMail Pty Ltd
  brong@xxxxxxxxxxxxxxxx


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