Questions regarding imaptest

[rub zorghy]

Hi,

The measurements were created under the following conditions :

• operating system : Red Hat Enterprise Linux Server release 6.6 (Santiago)
kernel in version 2.6.32-504.el6.x86_64
• virtual server (VMware) with an Intel(R) Xeon(R) 4vCPU E5649 x 2,526 GHz
(2 cores per virtual socket) and 4 GB RAM
• 7,200 RPM SATA 1TB (FC SAN IBM System Storage N3400)
• all file systems had been formated in ext4
• Dovecot v.2.0.9
• imaptest v.1.0.0
• LDAP 389 Directory Server v.1.2.2
• free pagecache, dentries and inodes: echo 3 > /proc/sys/vm/drop_caches
and services restarted before the test

"Tuning" based upon the book « *Dovecot: POP3/IMAP servers for enterprises
and ISPs* » Peer Heinlein :

 ---%<------------------------------------------

imap {} (10-master.conf).
service imap {
[...]
process_limit = 8192
[...]
}

auth {}
service auth {
[...]
client_limit = 9516
[...]
}

process_min_avail = 16

 ---%<------------------------------------------

mail_max_userip_connections = 100

The test results shows :

Logi List Stat Sele Fetc Fet2 Stor Dele Expu Appe Logo
100%  50%  50% 100% 100% 100%  50% 100% 100% 100% 100%
                          30%                  5%
 324  142  128  263  299  405   92  153  320  336  335 800/800
 212   92   92  182  166  233   59   87  178  201  202 800/800
 - 4051 stalled for 16 secs in command: 8 APPEND "INBOX" () {3251+}
 315  160  134  300  275  400   85  136  300  317  317 800/800
 - 4051 stalled for 17 secs in command: 8 APPEND "INBOX" () {3251+}
 247  130  163  292  251  366   99  115  239  240  240 800/800
 222  122  117  234  279  383  112  147  263  222  222 800/800
 188   93   94  177  168  232   65   87  162  196  195 800/800
 290  126  119  260  262  383  102  126  283  282  283 800/800
 240  125  107  243  259  353  102  130  253  256  256 800/800
 276  158  144  291  280  400  101  149  266  261  261 800/800
 254   95   89  189  235  313   78  118  243  253  253 800/800
  82  829  926  861  722  593  455  628 1695 2252    4 ms/cmd avg

Logi List Stat Sele Fetc Fet2 Stor Dele Expu Appe Logo
100%  50%  50% 100% 100% 100%  50% 100% 100% 100% 100%
                          30%                  5%
 148   59   55  126  119  174   43   64  130  147  147 800/800
 - 8770 stalled for 16 secs in command: 4 FETCH 1:2 (INTERNALDATE UID
INTERNALDATE)
 261  128  139  247  252  369  101  125  258  269  269 800/800
 302  159  158  307  282  398  109  126  296  298  297 800/800
 234   96  118  239  270  369   98  138  357  428  427 800/800
 361  213  220  450  383  596  151  197  240  165  166 800/800
 192   93   92  206  256  352  104  118  297  289  290 800/800
 - 9806 stalled for 16 secs in command: 4 FETCH 1 (RFC822.SIZE)
 245   85   72  162  128  190   52   73  157  174  173 800/800
 - 9806 stalled for 17 secs in command: 4 FETCH 1 (RFC822.SIZE)
 294  152  165  348  360  526  136  179  313  308  309 800/800
 272   87   79  174  164  229   54   85  218  230  230 800/800
 218  152  152  310  325  467  117  152  265  236  221 798/800
 119  830  852  859  707  566  511  702 1672 2161    6 ms/cmd avg

I have three questions :

1) how to interpret each row except the last one ?

2) how to explain the stalled commands ?

3) why benchmark shows too few read disk I/O ?

Thanks so much,

rub