Adding archiving to an existing Cyrus installation
Nic Bernstein
nic at onlight.com
Thu Nov 9 08:02:08 EST 2017
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:
* Create a filesystem snapshot
o zfs snapshot $ropt ${SOURCE_FS}@$newsnap
* Perform ZFS send/receive, something like this:
o zfs send -p $SENDVERBOSE $cloneorigin@$sourcestartsnap | zfs
recv -u $RECVVERBOSE -F "$destfs"
* Then, once we've completed a replication, we need to quiesce the
filesystem and do the same, again, to catch-up to current state
* Finally, replace the existing filesystem with the new replica, and
discard the original
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?
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.
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 at gmail.com
>> <mailto:reinaldoc at gmail.com>>:
>>
>> 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
>> <michael.menge at zdv.uni-tuebingen.de
>> <mailto:michael.menge at zdv.uni-tuebingen.de>
>>
>> :
>>
>>
>> Hi Nic,
>>
>> Quoting Nic Bernstein <nic at onlight.com
>> <mailto:nic at onlight.com>>:
>>
>> 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:
>> michael.menge at zdv.uni-tuebingen.de
>> <mailto:michael.menge at zdv.uni-tuebingen.de>
>> Wächterstraße 76
>> 72074 Tübingen
>>
>> ----
>> Cyrus Home Page: http://www.cyrusimap.org/
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>> To Unsubscribe:
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>>
>>
>>
>>
>> --------------------------------------------------------------------------------
>>
>> M.Menge Tel.: (49) 7071/29-70316
>> Universität Tübingen Fax.: (49) 7071/29-5912
>> Zentrum für Datenverarbeitung mail:
>> michael.menge at zdv.uni-tuebingen.de
>> <mailto:michael.menge at zdv.uni-tuebingen.de>
>> Wächterstraße 76
>> 72074 Tübingen
>>
>> ----
>> Cyrus Home Page: http://www.cyrusimap.org/
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>> To Unsubscribe:
>> https://lists.andrew.cmu.edu/mailman/listinfo/info-cyrus
>>
>>
>> --
>> Nic Bernstein nic at onlight.com <mailto:nic at onlight.com>
>> Onlight Inc. www.onlight.com
>> 6525 W Bluemound Rd., Ste 24 v. 414.272.4477
>> Milwaukee, Wisconsin 53213-4073 f. 414.290.0335
>>
>> ----
>> Cyrus Home Page: http://www.cyrusimap.org/
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>
> --
> Bron Gondwana, CEO, FastMail Pty Ltd
> brong at fastmailteam.com
>
>
>
>
> ----
> Cyrus Home Page: http://www.cyrusimap.org/
> List Archives/Info: http://lists.andrew.cmu.edu/pipermail/info-cyrus/
> To Unsubscribe:
> https://lists.andrew.cmu.edu/mailman/listinfo/info-cyrus
--
Nic Bernstein nic at onlight.com
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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