Yaoxing put forth on 12/22/2010 9:59 PM: > 3. 3.2MB/s disk IO write, 0.01MB/s read.
MB/s throughput isn't usually a factor, but IOPS definitely can be. What's in the iostat tps column for the device your mail queues reside on? If your mail queue resides on a single mechanical disk spindle you may be running into an IOPS limit. A single 7.2k rpm SATA disk can only sink approximately 150 seeks/sec (IOPS) under optimal conditions. You didn't mention the size of your subscriber base, but you mentioned that you queue mail to those subscriuber addresses every 4 seconds. If using a single SATA disk as described above, you will run out of IOPS with ~600 subscribers. If all of your queues and your log files, and your entire *nix system, resides on such a single disk, you'll run out of IOPS well below 600 subscribers. After investigating, if this is indeed the cause of your queue performance problem, the solution is to put the Postfix queues on a separate storage device, optimally for performance and cost reasons, and SSD. Using a dedicated device for the queue files, a single 15k SAS disk can sink approximately 300 seeks/sec (IOPS) which would allow for approximately 1200 subscribers with a 4 sec interval between mailings. A RAID 10 set of 4 such drives will allow double that amount, or 2400 subscribers. The cost of a good quality high performance SSD for Postfix queues is much less than 15k rpm SAS drives and far less than RAID 10, and will give you tens of thousands of IOPS, allowing for many thousands of subscribers, limited by SSD capacity. If your problem is limited IOPS, I suggest putting your queues on one of these: http://www.newegg.com/Product/Product.aspx?Item=N82E16820227610 If your total queue size is exceeding 40GB before mail can be flushed to the destinations, OCZ offers both 60GB and 90GB models for less than $200 USD. IOPS performance for all 3 sizes of OCZ devices is similar, around 4k Random Write (Aligned): 45,000-50,000 IOPS. An SSD such as this is by far the best price/performance solution to such a queue IOPS problem, if that is indeed your queue performance issue. -- Stan
