David Sterba wrote:
On Sat, Feb 11, 2012 at 05:49:41AM +0100, Timo Witte wrote:
What happened to the hot data tracking feature in btrfs? There are a lot
of old patches from aug 2010, but it looks like the feature has been
completly removed from the current version of btrfs. Is this feature
still on the roadmap?
Removed? AFAIK it hasn't been ever merged, though it's be a nice
feature. There were suggestions to turn it into a generic API for any
filesystem to use, but this hasn't happened.
The patches are quite independent and it was easy to refresh them on top
of current for-linus branch. A test run did not survive a "random"
xfstest, 013 this time, so I probably mismerged some bits. The patchset
lives in branch foreign/ibm/hotdatatrack in my git repo.
david
Someone recently mentioned bcache in another post who seems to cover
this subject fairly well. However would it not make sense if btrfs
actually was able to automatically take advantage of whatever disks is
added to the pool? For example if you have 10 disk of different size and
performance in a raid5/6 like configuration would it not be feasible if
btrfs automagically (option) could manage it's own cache? For example it
could reserve a chunk of free space as cache (based on how much data is
free) and stripe data over all disks (cache). When the filesystem
becomes idle or at set intervals it could empty the cache or
move/rebalance pending writes over to the original raid5/6 like setup.
As far as I remember hot data tracking was all about moving the data
over to the fastest disk. Why not utilize all disks and benefit from
disks working together?
Svein Engelsgjerd
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