Date: Thu, 06 Sep 2001 23:35:48 +0200 From: Sheldon Hearn <sheldonh@starjuice.net> To: freebsd-hardware@FreeBSD.org Subject: Low-latency SCSI solution Message-ID: <73468.999812148@axl.seasidesoftware.co.za>
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Hi folks, Right now, the bottleneck on my mail servers is disk IO latency. By turning off the use of fsync() in the MTA (exim) and queuing the mail for an entire mailshot (100,000 to 550,000 messages) before commencing delivery, I've managed to drop the average seek time (msps) to 7ms. This limits me to a delivery rate of around 50,000 messages per hour. I'm about to order more storage for these beasts and wondered what the best avenue might be. I've heard good things about the Mylex RAID controllers. I've also heard good things about the new 15,000rpm Seagates. *) RAID 0 or RAID 0+1 because performance for this volume is more important than fault tolerance. If I encounter disk failure during a mailshot, it's not the end of the world if the entire mailshot aborts, provided disk failures don't happen often. :-) *) Cheetah SCSI X15 (15,000rpm) drives, because low seek time (3.9ms) is more important than high throughput. *) A small stripe size. *) Ideally, the array should use write-back caching, but use a UPS. This is all based on reading, not experience. Any advice from people with real experience in combatting storage IO latency? Ciao, Sheldon. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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