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Does Ext4 support parallel write similar to XFS?

To: xfs@xxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, LKML <linux-kernel@xxxxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Does Ext4 support parallel write similar to XFS?
From: Amit Sahrawat <amit.sahrawat83@xxxxxxxxx>
Date: Wed, 25 Jan 2012 10:49:59 +0530
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In XFS we can write parallel (i.,e we can make use of allocation
groups for writing process). If the files are kept in individual
directories, there is a possibility that first the blocks for that
files be used from individual allocation groups. If I start ‘4’
writing process(cp 100MB_file /<dirnum>/) – after writing is finished
– if I check the bmap – it does shows that initial allocation was from
individual allocation groups.
Even though in Ext4 also we do have groups – but I am not able to get
behavior similar to XFS.
If I check the file extents – the extents are in mixed form, the
allocation pattern is also very fragmented.

Please share more on this. Also, if there is a possible exact test
case to check for parallel writes support.

Thanks & Regards,
Amit Sahrawat

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