On Mon, 7 Apr 2014 11:11:11 AM Austin S Hemmelgarn wrote: > This is because every other filesystem (except ZFS) doesn't use COW > semantics.
There is an interesting article on LWN at the moment (subscriber only for the next day or two, but if you can afford it I'd suggest considering subscribing) about the Linux Storage, Filesystem, and Memory Management (LSFMM) Summit discussions around the impact of the new Shingle Magnetic Recording (SMR) drives that may change that. Given these devices are likely to have large sequential write only areas it's going to make getting existing Linux filesystems to work on them "interesting", in the section on Dave Chinners filesystem part of the discussion it says: # Any of the existing filesystems that do not support copy-on-write (COW) # cannot really be optimized for SMR, he said, because you can't overwrite # data in sequential zones. That would mean adding COW to ext4 and XFS, # Chinner said. https://lwn.net/Articles/592091/ There's some background to SMR drives (available to all) from the LSFMM here: https://lwn.net/Articles/591782/ All the best, Chris -- Chris Samuel : http://www.csamuel.org/ : Melbourne, VIC
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