September 2020 - dovecot

Btrfs RAID-10 performance
by Miloslav Hůla 15 Sep '20

15 Sep '20

Hello, I sent this into the Linux Kernel Btrfs mailing list and I got reply: "RAID-1 would be preferable" (https://lore.kernel.org/linux-btrfs/7b364356-7041-7d18-bd77-f60e0e2e2112@le…) May I ask you for the comments as from people around the Dovecot? We are using btrfs RAID-10 (/data, 4.7TB) on a physical Supermicro server with Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz and 125GB of RAM. We run 'btrfs scrub start -B -d /data' every Sunday as a cron task. It takes about 50 minutes to finish. # uname -a Linux imap 4.9.0-12-amd64 #1 SMP Debian 4.9.210-1 (2020-01-20) x86_64 GNU/Linux RAID is a composition of 16 harddrives. Harddrives are connected via AVAGO MegaRAID SAS 9361-8i as a RAID-0 devices. All harddrives are SAS 2.5" 15k drives. Server serves as a IMAP with Dovecot 2.2.27-3+deb9u6, 4104 accounts, Mailbox format, LMTP delivery. We run 'rsync' to remote NAS daily. It takes about 6.5 hours to finish, 12'265'387 files last night. Last half year, we encoutered into performace troubles. Server load grows up to 30 in rush hours, due to IO waits. We tried to attach next harddrives (the 838G ones in a list below) and increase a free space by rebalace. I think, it helped a little bit, not not so rapidly. Is this a reasonable setup and use case for btrfs RAID-10? If so, are there some recommendations to achieve better performance? Thank you. With kind regards Milo # megaclisas-status -- Controller information -- -- ID | H/W Model | RAM | Temp | BBU | Firmware c0 | AVAGO MegaRAID SAS 9361-8i | 1024MB | 72C | Good | FW: 24.16.0-0082 -- Array information -- -- ID | Type | Size | Strpsz | Flags | DskCache | Status | OS Path | CacheCade |InProgress c0u0 | RAID-0 | 838G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdq | None |None c0u1 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sda | None |None c0u2 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdb | None |None c0u3 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdc | None |None c0u4 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdd | None |None c0u5 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sde | None |None c0u6 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdf | None |None c0u7 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdg | None |None c0u8 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdh | None |None c0u9 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdi | None |None c0u10 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdj | None |None c0u11 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdk | None |None c0u12 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdl | None |None c0u13 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdm | None |None c0u14 | RAID-0 | 558G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdn | None |None c0u15 | RAID-0 | 838G | 256 KB | RA,WB | Enabled | Optimal | /dev/sdr | None |None -- Disk information -- -- ID | Type | Drive Model | Size | Status | Speed | Temp | Slot ID | LSI ID c0u0p0 | HDD | SEAGATE ST900MP0006 N003WAG0Q3S3 | 837.8 Gb | Online, Spun Up | 12.0Gb/s | 53C | [8:14] | 32 c0u1p0 | HDD | HGST HUC156060CSS200 A3800XV250TJ | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 38C | [8:0] | 12 c0u2p0 | HDD | HGST HUC156060CSS200 A3800XV3XT4J | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 43C | [8:1] | 11 c0u3p0 | HDD | HGST HUC156060CSS200 ADB05ZG4XLZU | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 46C | [8:2] | 25 c0u4p0 | HDD | HGST HUC156060CSS200 A3800XV3DWRL | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 48C | [8:3] | 14 c0u5p0 | HDD | HGST HUC156060CSS200 A3800XV3XZTL | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 52C | [8:4] | 18 c0u6p0 | HDD | HGST HUC156060CSS200 A3800XV3VSKJ | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 55C | [8:5] | 15 c0u7p0 | HDD | SEAGATE ST600MP0006 N003WAF1LWKE | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 56C | [8:6] | 28 c0u8p0 | HDD | HGST HUC156060CSS200 A3800XV3XTDJ | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 55C | [8:7] | 20 c0u9p0 | HDD | HGST HUC156060CSS200 A3800XV3T8XL | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 57C | [8:8] | 19 c0u10p0 | HDD | HGST HUC156060CSS200 A7030XHL0ZYP | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 61C | [8:9] | 23 c0u11p0 | HDD | HGST HUC156060CSS200 ADB05ZG4VR3P | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 60C | [8:10] | 24 c0u12p0 | HDD | SEAGATE ST600MP0006 N003WAF195KA | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 60C | [8:11] | 29 c0u13p0 | HDD | SEAGATE ST600MP0006 N003WAF1LTZW | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 56C | [8:12] | 26 c0u14p0 | HDD | SEAGATE ST600MP0006 N003WAF1LWH6 | 558.4 Gb | Online, Spun Up | 12.0Gb/s | 55C | [8:13] | 27 c0u15p0 | HDD | SEAGATE ST900MP0006 N003WAG0Q414 | 837.8 Gb | Online, Spun Up | 12.0Gb/s | 47C | [8:15] | 33 # btrfs --version btrfs-progs v4.7.3 # btrfs fi show Label: 'DATA' uuid: 5b285a46-e55d-4191-924f-0884fa06edd8 Total devices 16 FS bytes used 3.49TiB devid 1 size 558.41GiB used 448.66GiB path /dev/sda devid 2 size 558.41GiB used 448.66GiB path /dev/sdb devid 4 size 558.41GiB used 448.66GiB path /dev/sdd devid 5 size 558.41GiB used 448.66GiB path /dev/sde devid 7 size 558.41GiB used 448.66GiB path /dev/sdg devid 8 size 558.41GiB used 448.66GiB path /dev/sdh devid 9 size 558.41GiB used 448.66GiB path /dev/sdf devid 10 size 558.41GiB used 448.66GiB path /dev/sdi devid 11 size 558.41GiB used 448.66GiB path /dev/sdj devid 13 size 558.41GiB used 448.66GiB path /dev/sdk devid 14 size 558.41GiB used 448.66GiB path /dev/sdc devid 15 size 558.41GiB used 448.66GiB path /dev/sdl devid 16 size 558.41GiB used 448.66GiB path /dev/sdm devid 17 size 558.41GiB used 448.66GiB path /dev/sdn devid 18 size 837.84GiB used 448.66GiB path /dev/sdr devid 19 size 837.84GiB used 448.66GiB path /dev/sdq # btrfs fi df /data/ Data, RAID10: total=3.48TiB, used=3.47TiB System, RAID10: total=256.00MiB, used=320.00KiB Metadata, RAID10: total=21.00GiB, used=18.17GiB GlobalReserve, single: total=512.00MiB, used=0.00B I do not attach whole dmesg log. It is almost empty, without errors. Only lines about BTRFS are about relocations, like: BTRFS info (device sda): relocating block group 29435663220736 flags 65 BTRFS info (device sda): found 54460 extents BTRFS info (device sda): found 54459 extents

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[BUG] GSSAPI auth doesn't work on 2.3.11
by Carlos Mogas da Silva 15 Sep '20

15 Sep '20

Hi list! I have a CentOS 7 server running dovecot with GSSAPI auth enabled. Version 2.3.10 was working fine but after the upgrade to 2.3.11 it stopped working. On thing I see on the logs is that the user field comes up empty when compared to the 2.3.10. Example: 2.3.10: Sep 14 13:39:20 mail.r3pek.org dovecot[10189]: imap-login: Login: user=<r3pek(a)r3pek.org>, method=GSSAPI, rip=xxxx, lip=2a01:4f8:1c17:61c0::1, mpid=10195, TLS, session=<PaDSUkWvAOkgAQgY3LZuALKwbzMw3BW/> 2.3.11: Sep 14 12:19:24 mail.r3pek.org dovecot[9264]: imap-login: Disconnected (auth failed, 1 attempts in 6 secs): user=<>, method=GSSAPI, rip=2001:818:dcb6:6e00:b2b0:6f33:30dc:15bf, lip=2a01:4f8:1c17:61c0::1, TLS, session=<pRubNESvMuQgAQgY3LZuALKwbzMw3BW/> Reverting back to 2.3.10 confirmed it's a 2.3.11 thing. Is there any change necessary after the upgrade to 2.3.11 or is this really a bug?

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Is it possible to only replicate indexes and not the mail data
by Marc Roos 14 Sep '20

14 Sep '20

Is it possible to only replicate indexes and not the mail data? (Because the data is already on distributed storage)

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logging LMTP activity
by Janis 11 Sep '20

11 Sep '20

Hello, I've been trying to set up Postfix + Dovecot LMTP setup. Basic idea taken from https://wiki2.dovecot.org/HowTo/PostfixDovecotLMTP, but since Postfix is on different host inet listener is used instead of unix socket. Message delivery works. Messages are delivered to correct mailboxes, if they exist. But the problem is with logging on Dovecot side; i can not get any lmtp logs at all. I kind of expected that i could get logs about: 1) Postfix has connected and delivering mail to mail(a)address.com, 2) If mailbox does not exists, would expect to see in logs the reason for rejection - mailbox does not exist 3) any other useful info would be nice as well. How do you get LMTP to log something? My Dovecot version is 2.3.11.3. Basic IMAP logging is working. I see when users have connected, etc. I tried as suggested at https://doc.dovecot.org/configuration_manual/protocols/lmtp_server/#logging If the given logging example block is used in configuration, i get no logs in file /var/log/dovecot-lmtp.log. I thought maybe file is not created automatically, so i tried to create it myself as well. Does not work. chmod 0777 does not either, chown to dovecot:dovecot neither. In a way i am curious about "executable = lmtp -L" part. What is -L flag? Are there any more flags? Where could i learn about them? I have read all the docs that come with the buld and mention something of lmtp, it's basically wiki, i guess... but i could not find any helpful info. I found that file lmtp is at /usr/local/libexec/dovecot/lmtp. When i execute it with -L flag it works. Other flags don't. The problem is that there are no -h or --help flags. Then i tried raw logging as described here: https://doc.dovecot.org/admin_manual/debugging/debugging_rawlog/#debugging-… As i understand, only 4th possibility is applicable to LMTP, am i right? 2nd kind of seems maybe somehow could be usable, but i don't see how... It is not clearly stated in wiki where "lmtp_rawlog_dir" should be added, but i add it within "protocol lmtp { .. }" block, similar as imap. Does not work for me - no logs while messages arrive. The catchy part in wiki is that for imap special arguments are used "-R rawlog" in service imap-login, postlogin. But i don't see any lmtp-login or such service available. So should it work only with "lmtp_rawlog_dir" option? What could i be doing wrong? Does anyone have working lmtp configuration with logging available? Thank you very much! I am sorry that my message is so long, but i tried even more to get it working... :) Any help or idea of how to better debug the situation or search for solution is kindly appreciated.

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Re: Doveadm error since 2.3.11.3 when run as unprivileged user
by Olav Seyfarth 11 Sep '20

11 Sep '20

On Thu, Aug 13, 2020, Arjen de Korte wrote: > include optional config file and suppress errors if it doesn't exist I followed this workaround, which is nicely summarized at https://github.com/postfixadmin/postfixadmin/issues/381#issuecomment-678269… Yet, not all errors are suppressed this way: $ doveadm pw doveadm(olav): Error: net_connect_unix(/run/dovecot/stats-writer) failed: Permission denied $ ls -l /run/dovecot/stats-writer srw-rw---- 1 root dovecot 0 11. Sep 00:27 stats-writer Olav

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Re: Btrfs RAID-10 performance
by Robert Nowotny 11 Sep '20

11 Sep '20

"Miloslav" == Miloslav Hůla <miloslav.hula(a)gmail.com> <miloslav.hula(a)gmail.com> writes: Miloslav> Dne 09.09.2020 v 17:52 John Stoffel napsal(a): Miloslav> There is a one PCIe RAID controller in a chasis. AVAGO Miloslav> MegaRAID SAS 9361-8i. And 16x SAS 15k drives conneced to Miloslav> it. Because the controller does not support pass-through for Miloslav> the drives, we use 16x RAID-0 on controller. So, we get Miloslav> /dev/sda ... /dev/sdp (roughly) in OS. And over that we have Miloslav> single btrfs RAID-10, composed of 16 devices, mounted as Miloslav> /data. I will bet that this is one of your bottlenecks as well. Get a secord or third controller and split your disks across them evenly. Miloslav> That's plan for a next step. Miloslav> We run 'rsync' to remote NAS daily. It takes about 6.5 hours to finish, Miloslav> 12'265'387 files last night. That's.... sucky. So basically you're hitting the drives hard with random IOPs and you're probably running out of performance. How much space are you using on the filesystem? Miloslav> It's not so sucky how it seems. rsync runs during the Miloslav> night. And even reading is high, server load stays low. We Miloslav> have problems with writes. Ok. So putting in an SSD pair to cache things should help. And why not use brtfs send to ship off snapshots instead of using rsync? I'm sure that would be an improvement... Miloslav> We run backup to external NAS (NetApp) for a disaster Miloslav> recovery scenario. Moreover NAS is spreaded across multiple Miloslav> locations. Then we create NAS snapshot, tens days Miloslav> backward. All snapshots easily available via NFS mount. And Miloslav> NAS capacity is cheaper. So why not run the backend storage on the Netapp, and just keep the indexes and such local to the system? I've run Netapps for many years and they work really well. And then you'd get automatic backups using schedule snapshots. Keep the index files local on disk/SSDs and put the maildirs out to NFSv3 volume(s) on the Netapp(s). Should do wonders. And you'll stop needing to do rsync at night. Miloslav> It's the option we have in minds. As you wrote, NetApp is very solid. Miloslav> The main reason for local storage is, that IMAP server is completely Miloslav> isolated from network. But maybe one day will use it. It's not completely isolated, it can rsync data to another host that has access to the Netapp. **grin** Miloslav> Unfortunately, to quickly fix the problem and make server Miloslav> usable again, we already added SSD and moved indexes on Miloslav> it. So we have no measurements in old state. That's ok, if it's better, then its better. How is the load now? Looking at the output of 'iostat -x 30' might be a good thing. Miloslav> Situation is better, but I guess, problem still exists. I Miloslav> takes some time to load be growing. We will see. Hmm... how did you setup the new indexes volume? Did you just use btrfs again? Did you mirror your SSDs as well? Do the indexes fill the SSD, or is there 20-30% free space? When an SSD gets fragmented, it's performance can drop quite a bit. Did you put the SSDs onto a seperate controller? Probably not. So now you've just increased the load on the single controller, when you really should be spreading it out more to improve things. Another possible hack would be to move some stuff to a RAM disk, assuming your server is on a UPS/Generator incase of power loss. But that's an unsafe hack. Also, do you have quotas turned on? That's a performance hit for sure. Miloslav> Thank you for the fio tip. Definetly I'll try that. It's a good way to test and measure how the system will react. Unfortunately, you will need to do your testing outside of normal work hours so as to not impact your users too much. Good luck! Please post some numbers if you get them. If you see only a few disks are 75% or more busy, then **maybe** you have a bad disk in the system, and moving off that disk or replacing it might help. Again, hard to know. Rebalancing btrfs might also help, especially now that you've moved the indexes off that volume. Robert: Fio is an acronym for *Flexible IO Tester* and describes a tool for measuring IO performance. With Fio, devices such as hard drives or SSDs can be tested for their speed by executing a *user-defined **workload* and collecting performance data. Therefore it might be difficult to really simulate the load with that, because You need to define the workload Yourself. But, at least, You might use it to get an idea of maximum transfer rates, random I/O etc. *iotop* shows the *current I/O transfer **rates* for the currently running processes / threads. It uses the I/O usage information of the Linux kernel, so it might be a good tool for You. *htop *might also be Your friend. and of course, as someone else pointed out : > Looking at the output of 'iostat -x 30' might be a good thing. my default setup for such diagnosis is to run iotop, htop, ntop to get an idea whats going on and measure ... for the index-SSD (on a different Channel ? NvMe ?) I strongly suggest to compare EXT4 vs BTRFS - some Benchmarks suggest that on fast SSD´s EXT4 is much (factor 4-5) faster then btrfs. You might also try ZSTD transparent compression on the remaining (non-SSD) btrfs disks - this can boost the transfer rate (since the data is compressed) if the Server CPU´s have enough juice. But from my guts feeling, its not the transfer rate - its the random I/O (in that case the situation will get worse with compression), but You really need to measure that. In general I dont understand that (old fashioned) configuration - using a bunch of 2TB or even 4TB TLC SSD in Raid10 is nowadays really affordable. You can keep the old disks for (local) rsync before You rsync from there to the NAS ... Robert

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Bug in sieve script compilation
by Иннокентий Сенновский 10 Sep '20

10 Sep '20

Hi, this is Rumata888 from hackerone. This is the other bug I found in sievec. If you try to compile the following script, it will result in a panic. The reason is: export expects its arguments to be either strings or lists of strings. When we issue an export command with a number immediately followed by an export command with a string argument, on parsing the second command sievec tries to merge the commands by merging the arguments. When it encounters an argument of unexpected type, it panics. Once again, I would advise unlinking invalid commands from ast, so that parsing of following commands was not dependent on previous irregularities.

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dbox alternate storage and archived namespace
by Daniel Miller 10 Sep '20

10 Sep '20

This may (and probably does) come under the heading of "really dumb ideas", but... Before I develop this further I need to ask - is it possible to have a "primary" mail_location using single-dbox with an alternate storage using multi-dbox? This is *not* the same as different storages for different namespaces (already have that). -- Daniel

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Re: zlib errors after upgrading to 2.3.11.3
by Robert Nowotny 09 Sep '20

09 Sep '20

On 8. Sep 2020, at 12.35, Robert Nowotny <rnowotny1966(a)gmail.com> wrote: Dear Aki, I switched to "gz" now, since "zstd" also gave some errors on writing to files. What kind of errors? Probably this? : Panic: file ostream.c: line 287 (o_stream_sendv_int): assertion failed: (!stream->blocking) can be - unfortunately I do not have the log files anymore... Sep 3 08:33:25 lxc-imap dovecot: imap(mpaul)<48684><2/9E5mKuAezAqKjk>: Error: Mailbox Sent: UID=2171: read(zlib(/home/vmail/virtualmailboxes/mpaul/storage/m.119)) failed: read(/home/vmail/virtualmailboxes/mpaul/storage/m.119) failed: Broken pipe (FETCH BODY[]) Also this way you can see if the broken mail is actually xz or zstd or zlib. It would be nice to know if there are any zstd or zlib compressed mails that have problems. We did a lot of stress testing with zstd and also with xz, but haven't been able to reproduce any problems. It's also strange that it says taht the error is "Broken pipe" - that doesn't indicate that the mail is corrupted but that there is something more strange going on. So perhaps you don't actually have any mails written as corrupted, but Dovecot is just somehow having trouble reading the mails. I managed to reproduce this. The files aren't corrupted, it's just that reading is failing. The attached patch should fix the xz code and should make your files readable again. Yes, it works ! I switched now to "zstd" compression and currently re-compressing all user imap folders (one by one) thank You so much ! Robert

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Leaked Events
by bobby 08 Sep '20

08 Sep '20

I am going through my maillog file, and noticed these events: Sep 8 15:56:17 mail dovecot[294462]: lmtp(391257): Warning: Event 0x55db5bc41200 leaked (parent=0x55db5bc3b830): mail-storage-service.c:1325 Sep 8 15:56:17 mail dovecot[294462]: lmtp(391257): Warning: Event 0x55db5bc3b830 leaked (parent=0x55db5bc34450): smtp-server-recipient.c:38 Sep 8 15:56:17 mail dovecot[294462]: lmtp(391257): Warning: Event 0x55db5bc34450 leaked (parent=0x55db5bc34130): connection.c:523 Sep 8 15:56:17 mail dovecot[294462]: lmtp(391257): Warning: Event 0x55db5bc34130 leaked (parent=0x55db5bc20ce0): smtp-server-connection.c:773 Sep 8 15:56:17 mail dovecot[294462]: lmtp(391257): Warning: Event 0x55db5bc20ce0 leaked (parent=(nil)): lmtp-client.c:164 Is this something to be concerned about?

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