Hi, We achieved considerable improvement in delivery speed and thereby negligible queues by shifting the mail spool to a faster disk.
Rgds/DP Sent from my iPhone. Pls excuse brevity and typos if any. > On 20-Apr-2018, at 8:10 PM, Stephen Satchell <l...@satchell.net> wrote: > >> On 04/20/2018 06:44 AM, Wietse Venema wrote: >> No, there is contention for the file system. >> If you disabled in_flow_delay, turn it back on, please. This allows >> the queue manager to push back, though it works only for clients >> that make few parallel connections. > > Looking at master.cf, there is the column "command + args". > > Question: would "nice -n 5 <command>" work? > > for example: > pickup unix n - n 60 1 nice -5 pickup > smtp inet n - n - 5 nice -5 smtpd > smtps inet n - n - - nice -5 smtpd > -o smtpd_tls_wrappermode=yes -o smtpd_sasl_auth_enable=yes > (submission, too?) > > This means that, on disk contention, the other processes have an edge over > the above-listed processes. As I recall, when you have multiple processes > contending for I/O on a device, the process with the higher working priority > gets selected. For writes, though, most of the requests end up being > buffered and the writes actually performed by a daemon or triggered by > close(2) or fsync(2). > > (All this goes out the window when one moves to solid-state disk. That > assumes that the system running PostFix can keep up with the inflow; if not, > then my suggestion may still have merit even with SSD.) > > In TUNING_README.html, you suggest running a DNS server on the local machine. > Excellent advice. When I configured an instance of Postfix as a smart relay > for a double-handful of CPanel/PLESK servers, I found that a local DNS server > with a large DNS cache had a profound positive effect on clearing out the > mail queue in a timely manner. The computer running this PostFix instance > had eight gigabytes of DRAM, which also let the Linux file system's cache > reduce the accesses to the disk drive. > > For high-traffic endpoints (aol.com, gmail.com, yahoo.com, &c) I also had > dedicated senders defined so that I could throttle mail to those endpoints to > prevent triggering anti-spam controls, with the rest going out the regular > way. >
