- dovecot - dovecot.org

Re: [Dovecot] Performance of Maildir vs sdbox/mdbox
by Lee Standen 09 Feb '12

09 Feb '12

On 18.01.2012 21:54, Timo Sirainen wrote: > On Wed, 2012-01-18 at 20:44 +0800, Lee Standen wrote: > >> I've been desperately trying to find some comparative performance >> information about the different mailbox formats supported by Dovecot >> in >> order to make an assessment on which format is right for our >> environment. > > Unfortunately there aren't really any. Everyone who seems to switch > to > sdbox/mdbox usually also change their hardware at the same time, so > there aren't really any before/after metrics. I've of course some > unrealistic synthetic benchmarks, but I don't think they are very > useful. > > So, I would also be very interested in seeing some before/after > graphs > of disk IO, CPU and memory usage of Maildir -> dbox switch in same > hardware. > > Maildir is anyway definitely worse performance then sdbox or mdbox. > mdbox also uses less NFS operations, but I don't know how much faster > (if any) it is with Netapps. We have bought new hardware for this project too, so we might not be able to help out massively on that front... we do have NFS operations monitored though so we should at least be able to compare that metric since the underlying storage operating system is the same. All NetApp hardware runs their Data ONTAP operating system, so the metrics are assured to be the same :) How about this... are there any tools available (that you know of) to capture real live customer POP3/IMAP traffic and replay it against a separate system? That might be a feasible option for doing a like-for-like comparison in our environment? We could probably get something in place to simulate the load if we can do something like that... >> * All mail storage presented via NFS over 10Gbps Ethernet (Jumbo >> Frames) >> >> * Postfix will feed new email to Dovecot via LMTP >> >> * Dovecot servers have been split based on their role >> >> - Dovecot LDA Servers (running LMTP protocol) >> >> - Dovecot POP/IMAP servers (running POP/IMAP protocols) > > You're going to run into NFS caching troubles with the above split > setup. I don't recommend it. You will see error messages about index > corruption with it, and with dbox it can cause metadata loss. > http://wiki2.dovecot.org/NFS http://wiki2.dovecot.org/Director That might be the one thing (unfortunately) which prevents us from going with the dbox format. I understand the same issue can actually occur on Dovecot Maildir as well, but because Maildir works without these index files, we were willing to just go with it. I will raise it again, but there has been a lot of push back about introducing a single point of failure, even though this is a perceived one. The biggest challenge I have at the moment if I try to sell the dbox format is providing some kind of data on the expected gains from this. If it's only a 10% reduction in NFS operations for the typical user, then it's probably not worth our while. > >> - LDA & POP/IMAP servers are segmented into geographically split >> groups >> (so no server sees every single mailbox) >> >> - Nginx proxy used to terminate customer connections, connections >> are >> redirected to the appropriate geographic servers > > Can the same mailbox still be accessed via multiple geographic > servers? > I've had some plans for doing this kind of access/replication using > dsync.. No, we're using the nginx proxy layer to ensure that if a user in Sydney (for example) tries to access a Perth mailbox, their connection is redirected (by nginx) to the Perth POP/IMAP servers. Postfix configuration is handling the same thing on the LMTP side. The requirement here is for all users to have the same settings regardless of location, but still be able to locate the email servers and data close to the customer. > >> * Apache Lucene indexes will be used to accelerate IMAP search for >> users > > Dovecot's fts-solr or fts-lucene? fts-solr. I've been using Lucene/Solr interchangeably when discussing this project with my peers :) > >> Our closest current live configuration (Qmail SMTP, Courier IMAP, >> Maildir) >> has 600K mailboxes and pushes ~ 35,000 NFS operations per second at >> peak >> >> Some of the things I would like to know: >> >> * Are we likely to see a reduction in IOPS/User by using Maildir >> alone under >> Dovecot? > > If you have webmail type of clients, definitely. For > Outlook/Thunderbird > you should still see improvement, but not necessarily as much. > > You didn't mention POP3. That isn't Dovecot's strong point. Its > performance should be about the same as Courier-POP3, but could be > less > than QMail-POP3. Although if many of your POP3 users keep a lot of > mails > on server it > Our existing systems run with about 21K concurrent IMAP connections at any one point in time, not counting Webmail POP3 runs at about 3600 concurrent connections, but since those are not long lived it's not particularly indicative of customer numbers. Vague recollection is something like 25% IMAP, 55-60% POP3, rest < 20% Webmail. I'd have to go back and check the breakdown again. >> * If someone can give some technical reasoning behind why mdbox does >> less >> IOPS than Maildir? > > Maildir renames files a lot. From new/ -> to cur/ and then every time > message flag changes. That's why sdbox is faster. Why mdbox should be > faster than sdbox is because mdbox puts (or should put) more mail > data > physically closer in disks to make reading it faster. > >> I understand some of the reasons for the mdbox IOPS question, but I >> need >> some more information so we can discuss internally and make a >> decision as to >> whether we're comfortable going with mdbox from day one. We're very >> familiar with Maidlir, and there's just some uneasiness internally >> around >> going to a new mail storage format. > > It's at least safer to first switch to Dovecot+Maildir to make sure > that > any problems you might find aren't related to the mailbox format.. Yep, I'm considering that. The flip side is that it's actually going to be difficult for us to change mail format once we've migrated into this system, but we have an opportunity for (literally) a month long testing phase beginning in Feb/March which will let us test as many possibilities as we can.

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[Dovecot] [PATCH] Bad boundary check in client_find_namespace
by Christoph Bussenius 09 Feb '12

09 Feb '12

Hi, while trying to investigate the bug I reported last week, I found that there is a broken boundary check in client_find_namespace in src/imap/imap-commands-util.c. The code is: /* make sure two hierarchy separators aren't next to each others */ for (p = storage_name+1; *p != '\0'; p++) { if (p[0] == ns->real_sep && p[-1] == ns->real_sep) { client_send_tagline(cmd, "NO Invalid mailbox name."); return NULL; } } The loop iterates over the string storage_name starting from its second byte. However, the string may be "". This is the case if you select the root of a namespace, like in "SELECT shared" or "SELECT shared/user1". In that case, the code will read past the end of the buffer from random memory until it finds a zero byte or a duplicate separator. This would fix it: diff -ru dovecot-2.0.15.orig/src/imap/imap-commands-util.c dovecot-2.0.15/src/imap/imap-commands-util.c --- dovecot-2.0.15.orig/src/imap/imap-commands-util.c 2011-08-02 12:29:37.000000000 +0200 +++ dovecot-2.0.15/src/imap/imap-commands-util.c 2011-09-26 18:33:16.121917759 +0200 @@ -81,7 +81,9 @@ } /* make sure two hierarchy separators aren't next to each others */ - for (p = storage_name+1; *p != '\0'; p++) { + for (p = storage_name; *p != '\0'; p++) { + if (p == storage_name) + continue; if (p[0] == ns->real_sep && p[-1] == ns->real_sep) { client_send_tagline(cmd, "NO Invalid mailbox name."); return NULL; Cheers, Christoph Bußenius -- Christoph Bußenius Rechnerbetriebsgruppe der Fakultäten Informatik und Mathematik TU München +49 89-289-18519 <> Raum 00.05.055 <> Boltzmannstr. 3 <> Garching

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[Dovecot] 2.0.14 doveadm proxy list segfault
by Tom Pawlowski 09 Feb '12

09 Feb '12

Hi Timo, Periodic segfaults with doveadm proxy list: root@director1:~) doveadm proxy list doveadm(root): Error: LIST failed: Disconnected Segmentation fault (core dumped) Sometimes it's just the 'LIST failed' error, other times it's the error with the segfault. Usually the first attempt to call it works, subsequent attempts fail. I've attached a strace log of it in action. -- Tom Pawlowski OIT-CSS System Administrator office: Hill 147 email: tompru(a)jla.rutgers.edu phone: (732) 445-2634

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[Dovecot] Syncing shared mailboxes
by Knud Dombrowsky 09 Feb '12

09 Feb '12

Hi, while trying to sync the mailboxes of several users who use and share their mailboxes dsync prints this message: dsync-local(<user-who-uses-shared-mailbox>): Warning: Subscriptions file /home/<user-who-uses-shared-mailbox>/Maildir/subscriptions: Removing invalid entry: shared/<sharing-user>/<shared-folder> The problem is: Every user has to subscribe the shared folder again after each run of dsync... Is dsync capable of syncing shared mailboxes? Are there any preliminaries to do so? thanks in advance, Knud

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[Dovecot] crash on shared folders if remote user has empty $home
by Peer Heinlein 09 Feb '12

09 Feb '12

Hi, in seldom cirumstances it's possible that the imap-process is crashing without write something usefule into the logfile. a) User foo exists, is happy and everything's alright b) He had a shared folder given from bar c) In our setup we have mailforwarding adresses without a valid $home in LDAP c) if user bar is changed from a user with into a mailforwarding adress, the user foo won't have an entry for $home any more, but still exists in LDAP. d) If foo logs in, dovecot's exploring the shared folders given from the non-existing user bar. But bar's entry in LDAP doesn't have $home any more. imap crashes and closes the TCP-connection immediately. root@dobby2:/etc/dovecot# telnet xxxxxxxx 143 Escape character is '^]'. * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE ACL UIDPLUS STARTTLS AUTH=PLAIN AUTH=LOGIN AUTH=CRAM-MD5 AUTH=DIGEST-MD5] Dovecot ready. Testing. a LOGIN foo xxxxx a OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS MULTIAPPEND UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS ACL UIDPLUS QUOTA ACL RIGHTS=texk] Logged in a LIST "" "*" * BYE Internal error occurred. Refer to server log for more information. Connection closed by foreign host. Dec 22 21:57:41 dobby2 dovecot: master: Error: service(imap): child 18095 killed with signal 11 (core dumps disabled) e) This happens if mail_location=mdbox:%%h/mdbox is set in the shared folder namespace. If I set "mail_location=auto:" then Dovecot logs an error message, but is still possible to continue without any problems. Dec 22 21:33:59 dobby2 dovecot: imap(bar): Error: Namespace 'shared/bar/': Autodetection failed for auto: (home=/mail/foo/) -- Heinlein Professional Linux Support GmbH Linux: Akademie - Support - Hosting http://www.heinlein-support.de Tel: 030 / 40 50 51 - 0 Fax: 030 / 40 50 51 - 19 Zwangsangaben lt. §35a GmbHG: HRB 93818 B / Amtsgericht Berlin-Charlottenburg, Geschäftsführer: Peer Heinlein -- Sitz: Berlin

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[Dovecot] LSUB and subscribed folders
by Peer Heinlein 09 Feb '12

09 Feb '12

I have a strange behavior on a customer's server and I don't understand that: User "bar" has some folders and one shared folder from "foo" if I use the "LIST"-command, which should list AFAIK *all* folders: # telnet localhost 143 a login bar xxxx a OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS MULTIAPPEND UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS ACL RIGHTS=texk] Logged in a LIST "" "*" * LIST (\HasNoChildren) "/" "Gesendete Objekte" * LIST (\HasNoChildren) "/" "Papierkorb" * LIST (\HasNoChildren) "/" "INBOX" * LIST (\HasNoChildren) "/" "Trash" * LIST (\HasNoChildren) "/" "Entw&APw-rfe" * LIST (\HasNoChildren) "/" "Spam" * LIST (\Noselect \HasChildren) "/" "shared/foo" * LIST (\HasNoChildren) "/" "shared/foo/INBOX" a OK List completed. Using the LSUB-command, which should only list subscribed folders I can see some more shared folders. AFAIK the output of LSUB must be always less then LIST: a LSUB "" "*" * LSUB () "/" "Entw&APw-rfe" * LSUB () "/" "Gesendete Objekte" * LSUB () "/" "INBOX" * LSUB () "/" "Papierkorb" * LSUB () "/" "Spam" * LSUB () "/" "Trash" * LSUB (\Noselect) "/" "shared/amerkel" * LSUB () "/" "shared/foo/Papierkorb/Ungelesene Mails" * LSUB () "/" "shared/foo/INBOX" * LSUB () "/" "shared/foo/INBOX/abc/Unterebene 1" * LSUB () "/" "shared/foo/INBOX/abc/Unterebene 1/Test6789" * LSUB () "/" "shared/foo/INBOX/abc/Unterebene 1/Test Unterornder" * LSUB () "/" "shared/foo/INBOX/abc/Unterebene 1/Tsfgnksfgnk" a OK Lsub completed. a logout * BYE Logging out a OK Logout completed. And why is /shared/foo/INBOX listed with "HasNoChildren"? IMHO that's looking buggy. And, btw: Looks like's not possible to use the "doveadm"-command to get a list of a user's complete folder list. Maybe "doveadm mailbox" should get some extra parameters to geht all folders / only subscribe folders / only shared folders: # doveadm mailbox list -u bar Gesendete Objekte Papierkorb INBOX Trash Entwürfe Spam -- Heinlein Professional Linux Support GmbH Linux: Akademie - Support - Hosting http://www.heinlein-support.de Tel: 030/405051-42 Fax: 030/405051-19 Zwangsangaben lt. §35a GmbHG: HRB 93818 B / Amtsgericht Berlin-Charlottenburg, Geschäftsführer: Peer Heinlein -- Sitz: Berlin

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[Dovecot] doveadm altmove fails to pack messages?
by Lauri Alanko 09 Feb '12

09 Feb '12

Hello again. When I use doveadm altmove, I notice that it may result in some very small storage files in either the primary or the alternate storage location. I'm not quite sure, but it almost seems like every storage file that contains messages to be moved is simply split into two parts, even if a part might only contain a single message. This seems quite curious, since the idea of mdbox is after all to store as many messages in a single file as fits in mdbox_rotate_size, and dovecot-lda can quite successfully append messages to existing storage files. So why can't doveadm altmove? Is this the expected behavior, or is there something wrong with my setup? Thanks again, Lauri

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[Dovecot] force-resync fails to recover all messages in mdbox
by Lauri Alanko 09 Feb '12

09 Feb '12

To my understanding, when using mdbox, doveadm force-resync should be able to recover all the messages from the storage files alone, though of course losing all metadata except the initial delivery folder. However, this does not seem to be the case. For me, force-resync creates only partial indices that lose messages. The message contents are of course still in the storage files, but dovecot just doesn't seem to be aware of some of them after recreating the indices. Here is an example. I created a test mdbox by syncing a mailing list folder from a mbox location: $ dsync -m haskell-cafe backup mdbox:~/dbox Then I switched the location to the new mdbox: $ /usr/sbin/dovecot -n # 2.0.15: /etc/dovecot/dovecot.conf # OS: Linux 3.2.0-0.bpo.1-amd64 x86_64 Debian wheezy/sid mail_fsync = never mail_location = mdbox:~/dbox mail_plugins = zlib passdb { driver = pam } plugin { sieve = ~/etc/sieve/dovecot.sieve sieve_dir = ~/etc/sieve zlib_save = bz2 zlib_save_level = 9 } protocols = " imap" ssl_cert = </etc/ssl/certs/dovecot.pem ssl_key = </etc/ssl/private/dovecot.pem userdb { driver = passwd } protocol lda { mail_plugins = zlib sieve } Then I checked the number of messages we had in the new location: $ doveadm search all | wc 93236 186472 3625098 This was indeed the correct number, so the sync was fine: $ grep -c '^From .*..:..:.. ....$' ../mbox/haskell-cafe 93237 Then I removed all the indices and rebuilt them: $ mkdir bak $ mv mailboxes bak $ mv storage/dovecot.map.index* bak/ $ doveadm force-resync inbox doveadm(la): Warning: mdbox /home/la/dbox/storage: rebuilding indexes And what have we now: $ doveadm search all | wc 43864 87728 1699590 Somehow dovecot lost over half of the messages! This is really worrisome. It should always be possible to extract the plain mail content out from the storage, but currently it only _looks_ like it is possible: you get a problem in the indices, rebuild them, and then later migrate somewhere else. If you don't notice that you are missing mails, you may then eventually destroy the original mdbox storage files, thinking that their content is now safely elsewhere, when it really isn't. Lauri

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[Dovecot] Fedora 16 configuration
by Cliff Hayes 09 Feb '12

09 Feb '12

Hello, I am trying to get dovecot to work on a fedora 16 install with sendmail. I have been able to get it to work in the past with dovecot.conf but not with the new conf.d directory and associated config files. I keep seeing this in maillog: Feb 7 14:28:59 sendmail dovecot: pop3-login: Aborted login (no auth attempts): rip=x.x.x.x, lip=x.x.x.x And the mail client comes back with username or password invalid. Is there instructions somewhere regarding fedora 16 installs? I found this one and tried it to no avail: http://www.server-world.info/en/note?os=Fedora_16&p=mail&f=2 Thanks in advance, Cliff

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[Dovecot] openbsd and dovecot
by User Max 09 Feb '12

09 Feb '12

I'm setting up dovecot in OpenBSD OS. The problem is that I can't set up dovecot to use kerberos authentication via bsdauth which is "similar to pam" I try to test dovecot via telnet: telnet localhost pop3 user test +OK pass password -ERR [IN-USE] Temporary authentication failure and some strings from logs Feb 3 15:02:37 srv-mx-00 dovecot: auth: Error: bsdauth(rodin.m,127.0.0.1): getpwnam() failed: Operation not permitted Feb 3 15:02:46 srv-mx-00 dovecot: pop3-login: Disconnected (auth failed, 1 attempts): user=<rodin.m>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, secured Feb 3 15:29:13 srv-mx-00 dovecot: auth: Error: bsdauth(test,127.0.0.1): getpwnam() failed: Operation not permitted What am I doing wrong? Here is the output of dovecot -n auth_krb5_keytab = /etc/kerberosV/krb5.keytab auth_mechanisms = plain login default_internal_user = _dovecot default_login_user = _dovenull disable_plaintext_auth = no first_valid_gid = 2000 first_valid_uid = 2000 last_valid_gid = 2000 last_valid_uid = 2000 mail_gid = vmail mail_location = maildir:/var/vmail/%u%Ud/Maildir mail_uid = vmail mbox_write_locks = fcntl mmap_disable = yes passdb { driver = bsdauth } service auth { unix_listener /var/spool/postfix/private/auth { group = _postfix mode = 0666 user = _postfix } } ssl_cert = </etc/ssl/dovecotcert.pem ssl_key = </etc/ssl/private/dovecot.pem userdb { driver = passwd } userdb { args = uid=2000 gid=2000 home=/var/mail/%Lu driver = static } protocol imap { imap_client_workarounds = delay-newmail tb-extra-mailbox-sep tb-lsub-flags } protocol pop3 { pop3_client_workarounds = outlook-no-nuls oe-ns-eoh pop3_uidl_format = %08Xu%08Xv }

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