We are setting up a Dovecot over a pair of NFS which mirrored with DRBD +Heartbeat, under Debian Etch AMD64 with Kernel 2.6.22-5.

The problem was slow header downloading rate. We had tried to use
postal to inject 500 emails which are under 5KB each, but when ever we start up Mail.app, Thunderbird or even OE6, the
header download rate is terrible slow.

Its look like a few sec for just 1 header download from the strace of
the dovecot process, sometime, it maybe longer and this leading to the MUA hang.

We had tried dove 1.0.rc15-2etch3, 1.1beta13... and the following
configuration is for 1.1beta13.

Mount options on Dovecot frontend

nfs4 rsize=8192,wsize=8192,hard,fg,proto=tcp,retrans=0,noatime

Export option on NFS backend

/dap/mail
192.168.2.0 /24(rw,no_subtree_check,no_root_squash,no_all_squash,sync,fsid=0) /dap/mail/mstorage
192.168.2.0/24(rw,no_subtree_check,no_root_squash,no_all_squash,sync)

Dovecot Config dump.

base_dir = /var/run/dovecot/ protocols = pop3 imap disable_plaintext_auth = no log_path = /var/log/dovecot.log info_log_path = /var/log/dovecot-info.log log_timestamp = "%Y-%m-%d %H:%M:%S " ssl_disable = yes login_dir = /var/run/dovecot/login login_chroot = yes login_user = dovecot login_processes_count = 10 login_max_processes_count = 20 login_process_per_connection = yes mail_debug = yes max_mail_processes = 1024 mail_process_size = 256 mail_location = maildir:~/Maildir:INDEX=/var/indexes/%u (Indexes is
putting on local disk, but same with no luck) auth_process_size = 128 auth_cache_size = 32 auth_cache_ttl = 3600 auth_verbose = yes auth_debug = no auth_debug_passwords = no auth_worker_max_count = 50

namespace private { separator = / prefix = INBOX/ inbox = yes }

mail_extra_groups = mail mmap_disable = no lock_method = fcntl mail_nfs_storage = yes mail_nfs_index = no dotlock_use_excl = no fsync_disable = no

Strace Log file of dovecot during thunderbird download those headers.

17:19:27.670428 open("/dap/mstorage/example.com/dino/Maildir/cur/ 1201079181.H112920P11724.mx01.example.com,S=3841:2,", O_RDONLY) = 11 17:19:27.670631 fstat(11, {st_mode=S_IFREG|0600, st_size=3841, ...}) = 0 17:19:27.670691 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 3841 17:19:31.725525 pread(11, "", 255, 3841) = 0 17:19:31.725624 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 3841 17:19:31.725729 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 3841 17:19:31.725798 close(11) = 0

17:19:31.725887 open("/dap/mstorage/example.com/dino/Maildir/cur/ 1201079181.H210436P11742.mx01.example.com,S=2263:2,", O_RDONLY) = 11 17:19:31.726127 fstat(11, {st_mode=S_IFREG|0600, st_size=2263, ...}) = 0 17:19:31.726193 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 2263 17:19:38.973282 pread(11, "", 1833, 2263) = 0 17:19:38.973382 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 2263 17:19:38.973488 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 2263 17:19:38.973559 close(11) = 0

17:19:38.973645 open("/dap/mstorage/example.com/dino/Maildir/cur/ 1201079181.H210590P11751.mx01.example.com,S=3764:2,", O_RDONLY) = 11 17:19:38.973900 fstat(11, {st_mode=S_IFREG|0600, st_size=3764, ...}) = 0 17:19:38.973967 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 3764 17:19:39.013845 pread(11, "", 332, 3764) = 0 17:19:39.013906 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 3764 17:19:39.013999 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 3764 17:19:39.014066 close(11) = 0

17:19:39.014129 open("/dap/mstorage/example.com/dino/Maildir/cur/ 1201079181.H297801P11758.mx01.example.com,S=6890:2,", O_RDONLY) = 11 17:19:39.014331 fstat(11, {st_mode=S_IFREG|0600, st_size=6890, ...}) = 0 17:19:39.014391 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 4096 17:19:39.053878 pread(11, "~b_])!5b\'8rIwz/mmG31A}yr*9\'uC!$<"...,
4095, 4096) = 2794 17:19:39.053963 pread(11, "", 1301, 6890) = 0 17:19:39.054022 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 4096 17:19:39.054115 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 4096 17:19:39.054182 close(11) = 0

17:19:39.054245 open("/dap/mstorage/example.com/dino/Maildir/cur/ 1201079181.H308343P11761.mx01.example.com,S=2510:2,", O_RDONLY) = 11 17:19:39.054448 fstat(11, {st_mode=S_IFREG|0600, st_size=2510, ...}) = 0 17:19:39.054508 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 2510 17:19:42.805170 pread(11, "", 1586, 2510) = 0 17:19:42.805271 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 2510 17:19:42.805376 pread(11, "Return-path: dino@example.com\nE"...,
4096, 0) = 2510 17:19:42.805441 write(1, "* 272 FETCH (UID 3838 RFC822.SIZ"..., 2146)
= 2146 17:19:42.805503 close(11) = 0