Date: Sun, 24 Mar 2002 19:16:13 -0800 From: "Taylor Dondich" <thexder@lvcm.com> To: <chat@freebsd.org> Subject: Re: qmail (Was: Maintaining Access Control Lists ) Message-ID: <000c01c1d3ab$6d2c6960$6600a8c0@penguin> References: <F61GQUEYvZmDvHbYxPo0000a6bd@hotmail.com><20020323002608.B20699@rain.macguire.net><3C9C84CF.2090300@flash.net><20020323084327.A354@rain.macguire.net><3C9DF87D.5050306@cream.org> <p05101505b8c430e28572@[10.0.1.9]>
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I've got to say this was one of the most entertaining peices of e-mail I've read all day; furthermore, it was the most informative of them all. I just started using qmail as my mail delivery system of choice because sendmail was EXTREMELY difficult to configure in the ways that I wanted. I'm beginning to start up a webhosting service with virtual domain hosting with full e-mail services and qmail was frankly the only package out there with the commitment and features that seemed close to my liking. I was also looking at the other tools out there that I could slap on top of qmail to make it more functional (vpopmail, sqwebmail, etc). However, I do see your point of it's multitute of file processing tasks to handle just 1 peice of e-mail by it going in or out, I was at first in the impression of it being because of further redundancy in the system. I don't see this being a problem if you were processing a low amount of e-mail per day, however I could see the implications of this if your users went hogwild and started going crazy (disk activity would skyrocket). These are my thoughts, however I could be wrong. I'm still a fairly new newbie in the realm of FreeBSD and hope to get even further knowledgable in mailing, web, and dns services. BTW, I'm new to the list. Hi. Taylor Dondich ----- Original Message ----- From: "Brad Knowles" <brad.knowles@skynet.be> To: "Andrew Boothman" <andrew@cream.org>; "Benjamin Krueger" <benjamin@macguire.net> Cc: "Courtney Thomas" <ccthomas@flash.net>; <freebsd-chat@FreeBSD.ORG> Sent: Sunday, March 24, 2002 6:12 PM Subject: Re: qmail (Was: Maintaining Access Control Lists ) > At 4:02 PM +0000 2002/03/24, Andrew Boothman wrote: > > > I was interested about what you said about qmail and its author. > > I've recently started playing with qmail to investigate what mail > > server I prefer, but I agree that there is perhaps something a > > little strange about its author. I don't know what, perhaps its > > just that I find qmail.org such a weird site. > > The author of qmail is rightly considered to be one of the most > whacked-out kooks on the 'net. > > I've been on IETF mailing lists with him, and his attitude is > always that he is always right (by definition) and everyone else is > always wrong (by definition). He insists on replying to each and > every mail message posted to the list, and constantly dredging up old > points that everyone else has agreed were dead a long, long, long > time ago. > > He will reply to messages that are not anywhere near remotely > related to his favourite topic, quote some random line that is least > unlike the straw-man position that he wants to destroy, and then go > off on a multi-page rant. > > He considers himself to be God's gift to programming, security, > Internet mail, DNS, cryptography, and anything else he cares to > decide to screw around with, and woe betide anyone who ever disagrees > with his world-view -- even if that world-view changes and you used > to be his most vocal supporter. > > > The problem is that he is generally totally fscking clueless (at > least on all the topics with which I am familiar), and his > whacked-out ideas of how things should be done are non-solutions to > non-problems, and he simply doesn't understand what the real problems > are. > > > Let's take qmail as one example. Read the literature, and you > will find pretty universal agreement that the single biggest problem > with handling Internet e-mail is the issue of synchronous meta-data > updates, followed by synchronous data writes -- basically, you're > waiting on the disk, which is the single slowest device in the entire > system by many, many orders of magnitude, and the RFCs require you to > do things that mean that you can't really make much use of the kinds > of buffers and things you'd normally use to help insulate yourself > from such seriously heinous latency issues. > > The problem is that every time you create a file, delete a file, > or rename a file, the entire directory in which that file is located > must be locked for the exclusive use of that one process, for the > length of that directory operation. Now, you may be able to handle > these operations very quickly, but when you serialize all directory > operations in a busy mail queue, this starts to become a serious > problem. > > Compound this problem with the fact that you are required by the > RFCs to have committed the mail message to stable storage before you > respond to the sender "Okay, I've got it." You have to flush the > buffer for that file, and wait for the writes to complete before you > can proceed. You also have to flush the write buffer for the > directory before you can proceed (to ensure that the meta-data > updates are reliably written out). > > Now, it turns out that older versions of sendmail make this > problem doubly worse by using two files in /var/spool/mqueue for > every mail message -- a qf* file and a df* file (with others being > optional). This means twice as many files get created, written, > read, and deleted in a very short period of time (with appropriate > flushes of the buffers and waiting for the message to be committed to > stable storage before continuing, etc...). > > > But qmail makes this even worse -- it uses *three* files per > message! At least postfix is more intelligent and it uses only one > file (albeit in a proprietary format). > > Starting with version 8.12, sendmail has a new async I/O library > that allows it to avoid *ALL* synchronous meta-data updates in most > cases (i.e., those where the initial delivery attempt is successful). > It's kind of hard to beat zero synchronous meta-data updates. ;-) > > > More importantly, the author of postfix has relatively little ego > wrapped up in his programs, and if you can show him an error or an > incorrect assumption, he will generally listen to you. > > Do you know why no one has never collected the "bug bounty" that > the author of qmail has offered? Simple -- he has never publicly > acknowledged that any of his programs are less than 100% completely > and totally perfect, and any time someone does point out something > that is wrong, while he doesn't recognize it as a "bug", the problem > does seem to mysteriously get fixed in later releases. > > There's a lot more development going on with regards to sendmail, > and it may be more difficult to get them to listen to you. But I do > know that Eric, Greg, Claus, and crew do listen, because they are in > the process of eliminating every single major potential software > bottleneck that I identified in my "Sendmail Performance Tuning for > Large Systems" paper that I presented at SANE'98 (see > <http://www.shub-internet.org/brad/papers/sendmail-tuning/>). > > > I've got a whole laundry list (some twenty-three items by now) of > things that are wrong with tinydns and dnscache, and a lot of them > have to do with problems regarding the megalomaniacal author and his > unholy disciples. I will be writing them up, but I can't make any > guarantees as to when I'll be able to put them online. > > Even if I document my writings extensively with references to his > own web pages, documentation, etc... and the public writings of > others, I'm sure that he'll still file libel and slander charges > against me -- he does the same to anyone else who dares to speak out > against him, especially those who do so in a public forum. > > > God help you if you ever join the Church of Dan. And Dan help > you if you don't. > > -- > Brad Knowles, <brad.knowles@skynet.be> > > Do you hate Microsoft? Do you hate Outlook? Then visit the Anti-Outlook > page at <http://www.rodos.net/outlook/>; and see how much fun you can have. > > "They that can give up essential liberty to obtain a little temporary > safety deserve neither liberty nor safety." > -Benjamin Franklin, Historical Review of Pennsylvania. > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-chat" in the body of the message To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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