doveadm backup fails (compromised single attachment storage)

[Webert de Souza Lima]

Hi,

A couple of months ago I had a problem with Single Attachment Storage after
infrastructure migration;

All mailboxes were rsynced to another filesystem, and that may have broken
Single Attachment Storage. Many, many (if not all) mailboxes show the below
logs on dovecot:

imap(foo at bar.com): Error: read(attachments-connector(zlib(/dovecotdir/mail/
bar.com/foo/mailboxes/INBOX/dbox-Mails/u.26426))) failed:
read(/dovecotdir/attach/
bar.com/de/86/de8673894d6fb3f4460e3c26436eefa9a73517fa0f000452f553822367220761502e1d0ce220eee5aa9acf232df0adebf40cce90b57d2e60e1eb9c9ef21671fa-b0d3411772c14957536100009331bd36-43cea6154b3275573b0800009331bd36-26426[base64:19
b/l]) failed: open(/dovecotdir/attach/
bar.com/de/86/de8673894d6fb3f4460e3c26436eefa9a73517fa0f000452f553822367220761502e1d0ce220eee5aa9acf232df0adebf40cce90b57d2e60e1eb9c9ef21671fa-b0d3411772c14957536100009331bd36-43cea6154b3275573b0800009331bd36-26426)
failed: No such file or directory


When that happens, the MUA keeps syncing forever.

Now, I need to migrate all mailboxes (again) to another dovecot instance
(with no SAS), which works perfectly for new users but when I try to
migrate users from my current dovecot server for this new server, I get
such errors again, and I can't migrate:

2016-09-29T12:20:50.995934059Z Sep 29 12:20:50 dsync-server(foo at bar.com):
Error: dsync(cf7d091311eb):
read(attachments-connector(zlib(/dovecotdir/mdbox/bar.com/foo/storage/m.1)))
failed: read(/dovecotdir/attach/
bar.com/0c/df/0cdf86b1920938fe3a043f87e2ee9e63dda276bd5b9fba687e4a0c63d181c3b6ebdb96a9517f048c963db71404ad5d14e896e2e67b7abb0c9e107aed5c15ecf1-430ea904dff46757ba1700009331bd36[base64:18
b/l]) failed: open(/dovecotdir/attach/
bar.com/0c/df/0cdf86b1920938fe3a043f87e2ee9e63dda276bd5b9fba687e4a0c63d181c3b6ebdb96a9517f048c963db71404ad5d14e896e2e67b7abb0c9e107aed5c15ecf1-430ea904dff46757ba1700009331bd36)
failed: No such file or directory (last sent=mail, last recv=mail_request
(EOL))

Is there a way to fix the attachments problem? (I know I can't recover such
files, that's Ok)
Is there a way to migrate (dsync backup) ignoring such problems?

Thanks in advance.