Date: Thu, 26 Sep 2002 11:35:51 -0700 From: Claus Assmann <freebsd+current@esmtp.org> To: freebsd-current@FreeBSD.ORG Subject: Re: Journaled filesystem in CURRENT Message-ID: <20020926113551.A11092@zardoc.esmtp.org> In-Reply-To: <3D93459B.E4405568@mindspring.com>; from tlambert2@mindspring.com on Thu, Sep 26, 2002 at 10:36:27AM -0700 References: <200209251319.g8PDJYoD047918@ib.com.ua> <20020925111232.B3686@Odin.AC.HMC.Edu> <20020926111949.5c0da160.Alexander@Leidinger.net> <20020926090325.A24614@zardoc.esmtp.org> <3D93459B.E4405568@mindspring.com>
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On Thu, Sep 26, 2002, Terry Lambert wrote: > Claus Assmann wrote: > > When we tested several filesystems for mailservers (to store the > > mail queue), JFS and ext3 (in journal mode) beat UFS with softupdates > > by about a factor of 2. > > Hi Claus! Nice to hear from someone who actually tests things! > > I think that what you were probably testing was directory entry > layout and O(N) (linear) vs. O(log2(N)+1) search times for both > non-existant entries on creates, and for any entry on lookup > ( / 2 on lookup) . I doubt it. The number of files in the queue directories was fairly small during the runs. Moreover, ReiserFS showed fairly poor performance, even though it should be "good" for directory lookups, right? > The best answer for inbound mail is to go to per domain mail > queues, and the best for outbound is to go to hashed outbound > domains (as we discussed at the 2000 Sendmail MOTM gathering). > Per domain mail queues inbound give you a 100% hit rate on > a directory traversal for a queue flush; using hashed outbound > directories isn't a 100% hit rate, but you can keep it above > 85% with the right hashing structure, which makes the miss > rate have only 1-2% impact on processing. "Per domain" doesn't work easily if you have multiple recipients. Anyway, the new design clearly distinguishes between the content files and the data that is necessary for delivery. If someone is interested: http://www.sendmail.org/~ca/email/sm-9-rfh.html Just as a small data point: I get message acceptance rates of 400msgs/s on a journalling file system (using a "normal" PC) that writes the data into the journal too. AFAICT that's due to the fact that fsync() is much fast for this kind of storage. The important part for mailservers here is the rate at which content files can by safely written to disk. From my limited experience journalling file systems are here much better than softupdates. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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