Dear Aki,
I switched to "gz" now, since "zstd" also gave some errors on writing to files.
I dont know if "xz" compression or "zstd" shreddered my MDBOX Files, but I lost 4 days of mail. (a couple of thousand mails).
After restoring the backup (what was made after switching to version 2.3.11.3) I still have some broken mdfiles, but not too many.
Interestingly always in the "Sent" Mailbox on a number of Users.

I just can not go back to 20.08.2020 before I updated to 2.3.11.3 - too many emails would have been lost.

So - the current status is 2.3.11.3, with "gz" compression.

I force-synced and re-indexed all the mdbox files (250 GB), but still have some broken - please how can I fix those ?

You stated :

(In theory you could leave the existing mails xz-compressed, but best 
would be to re-compress everything via dsync so old mails can be read 
when we eventually remove xz support.)

what is the optimal way to do that, expecially not loosing the index (?) for outlook/thunderbird, for third party tools that rely on some index/hash (dunno how exactly that works) ?


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[])
Sep  3 08:35:26 lxc-imap dovecot: imap(mpaul)<48089><YRio1GKuEdHAqKi3>: 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[])
Sep  3 08:35:26 lxc-imap dovecot: imap(mpaul)<49228><p/0g9WKuVdHAqKi3>: 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[])
Sep  3 08:35:26 lxc-imap dovecot: imap(mpaul)<49229><GMAm9WKuVtHAqKi3>: 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[])
Sep  3 08:35:27 lxc-imap dovecot: imap(mpaul)<49230><YYot9WKuV9HAqKi3>: 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[])
...
Sep  3 09:04:44 lxc-imap dovecot: imap(cpotzinger)<49040></X+P72KuUNHAqKi3>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:04:51 lxc-imap dovecot: imap(cpotzinger)<54382><eYT1XWOux9HAqKi3>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:04:59 lxc-imap dovecot: imap(cpotzinger)<54396><nKllXmOuyNHAqKi3>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:05:06 lxc-imap dovecot: imap(cpotzinger)<54409><m2TOXmOuydHAqKi3>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:05:12 lxc-imap dovecot: imap(cpotzinger)<54422><IP86X2OuytHAqKi3>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
...
Sep  3 09:08:58 lxc-imap dovecot: imap(cpotzinger)<54867><BtGtbGOu49HAqKi3>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:19:15 lxc-imap dovecot: imap(mpaul)<56030></kHNkWOuAO3AqKjk>: 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[])
Sep  3 09:29:41 lxc-imap dovecot: imap(cpotzinger)<57274><c4rCtWOuKuzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:29:47 lxc-imap dovecot: imap(cpotzinger)<57320><K3Uqt2OuLOzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:29:54 lxc-imap dovecot: imap(cpotzinger)<57333><e4aMt2OuLezAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:30:01 lxc-imap dovecot: imap(cpotzinger)<57346><JEfzt2OuLuzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:30:08 lxc-imap dovecot: imap(cpotzinger)<57360><mH1YuGOuMOzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:30:14 lxc-imap dovecot: imap(cpotzinger)<57382><IzLBuGOuMezAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:30:21 lxc-imap dovecot: imap(cpotzinger)<57397><q10kuWOuM+zAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:30:27 lxc-imap dovecot: imap(cpotzinger)<57410><CSuJuWOuNOzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:31:22 lxc-imap dovecot: imap(mpaul)<57525><TfoOvWOuWO3AqKjk>: 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[])
Sep  3 09:31:49 lxc-imap dovecot: imap(cpotzinger)<57423><Be/ruWOuNuzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:31:55 lxc-imap dovecot: imap(cpotzinger)<57584><yvXOvmOuQuzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:32:02 lxc-imap dovecot: imap(cpotzinger)<57597><e/8tv2OuQ+zAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:32:08 lxc-imap dovecot: imap(cpotzinger)<57611><BLSOv2OuROzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:32:19 lxc-imap dovecot: imap(cpotzinger)<57633><Ky0twGOuR+zAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:32:26 lxc-imap dovecot: imap(cpotzinger)<57646><ljSRwGOuS+zAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:32:33 lxc-imap dovecot: imap(cpotzinger)<57659><rn75wGOuT+zAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:32:39 lxc-imap dovecot: imap(cpotzinger)<57672><GP9jwWOuUuzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:33:45 lxc-imap dovecot: imap(mpaul)<57795><2CEwxWOubu3AqKjk>: 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[])
Sep  3 09:38:29 lxc-imap dovecot: imap(mpaul)<58347><CKyX1mOuie3AqKjk>: 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[])
Sep  3 09:38:32 lxc-imap dovecot: imap(mpaul)<58352><osHU1mOuiu3AqKjk>: 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[])
Sep  3 09:38:44 lxc-imap dovecot: imap(cpotzinger)<54527><5ZpiYmOuBOfAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:38:51 lxc-imap dovecot: imap(cpotzinger)<58378><kAuN12OumuzAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
Sep  3 09:38:57 lxc-imap dovecot: imap(cpotzinger)<58392><xJLx12Oum+zAqKiU>: Error: Mailbox Sent: UID=29534: read(zlib(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703)) failed: read(/home/vmail/virtualmailboxes/cpotzinger/storage/m.4703) failed: Broken pipe (FETCH BODY[])
...

I had 4 broken mdbox files for 4 different users.
After deleting them, dovecot re-indexed, now everything is ok again.

I can try to update tonight again to 2.3.11.3 and see if some broken files will appear again tomorrow.

Am 25.08.2020 um 14:51 schrieb Aki Tuomi:

On 25/08/2020 14:35 Robert Nowotny <rnowotny@rotek.at> wrote:


I get ZLIB Errors after dovecot upgrade from 2.3.10.1 to 2.3.11.3


 Aug 21 15:27:34 lxc-imap dovecot: imap(acsida)<63870><jZk...>: Error: Mailbox Sent: UID=40826: read(zlib(/home/vmail/virtualmailboxes/acsida/storage/m.2409)) failed: read(/home/vmail/virtualmailboxes/acsida/storage/m.2409) failed: Broken pipe (FETCH BODY[])....
 
 many of those entries....
 
 after installing2.3.10.1 those files are still broken - but new files are working again.

 anything I can tweak or do ? 
 

Hi!

Is it possible your mdbox file is corrupted? Can you share doveconf -n?

Aki