Date: Thu, 7 Oct 1999 10:31:46 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: "Matthew D. Fuller" <fullermd@futuresouth.com> Cc: Peter Jeremy <peter.jeremy@alcatel.com.au>, Alfred Perlstein <bright@wintelcom.net>, freebsd-current@FreeBSD.ORG Subject: Re: make install trick Message-ID: <Pine.BSF.4.10.9910070953020.9776-100000@alphplex.bde.org> In-Reply-To: <19991006154419.O20768@futuresouth.com>
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> /dev/da0s1a on / (local, synchronous, writes: sync 32 async 15100) > ^^^^^^^^^^^ > > Though I'm still waiting for an explanation of WHY exactly I have async > writes on a sync partition. Nobody yet has said anything but 'that's > interesting...'. A direction to look would be helpful. The sync flag only affects data writes and block allocation for data writes. Metadata is normally always written synchronously, except for safe optimisations. Safe optimisations include never writing inode or block bitmaps (fsck can recover these), not writing some indirect blocks (correct block numbers are not very useful until the blocks have been written), and not writing inodes in many cases where only timestamps have changed. You seem to have a lot of async writes. This may be caused by using soft updates. Soft updates causes many (or most or all) metadata updates to be done using delayed writes. Using the sync flag with soft updates doesn't make much sense and may be harmfull (there doesn't seem to be anything to prevent data writes being done long before the metadata points to the data). Smaller number of async writes may be caused by metadata write optimisations. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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