Hi Zheng, * On Fri, Jan 13, 2012 at 04:41:16PM -0500, Zheng Da <zhengda1...@gmail.com> wrote:
Hello,I'm looking for a FS in Linux that supports concurrent direct IO write. ext4 supports concurrent direct IO read if we mount it with dioread_nolock, but doesn't support concurrent writes. XFS doesn't support concurrent direct IO at all. It locks the inode exclusive if it's direct IO. I tried btrfs, and it seems it doesn't support concurrent direct IO either though I haven't looked into its code. Is there a local FS that support concurrent direct IO write? It seems NFS supports it ( http://kevinclosson.wordpress.com/2011/08/12/file-systems-for-a-database-choose-one-that-couples-direct-io-and-concurrent-io-whats-this-have-to-do-with-nfs-harken-back-5-2-years-to-find-out/), but I'm looking for local FS. Thanks, Da
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XFS locks inode exclusive only if it is an unaligned Direct IO, which is apparently done to prevent race conditions -- refer to this http://oss.sgi.com/archives/xfs/2011-01/msg00157.html Also the behavior of Ext4 under dioread_nolock is supported by XFS by default and in a much better way. Also Ext4 is the only one which uses DIO_LOCKING while doing direct io.
Regards, -- Raghavendra Prabhu GPG Id : 0xD72BE977 Fingerprint: B93F EBCB 8E05 7039 CD3C A4B8 A616 DCA1 D72B E977 www: wnohang.net
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