From: Christian Stroetmann on
Hola Everybody;
On the 04.08.2010 19:40, Mingming Cao wrote:
> On Thu, 2010-07-29 at 22:17 +1000, Dave Chinner wrote:
>> On Wed, Jul 28, 2010 at 03:00:48PM -0700, Mingming Cao wrote:
>>> On Wed, 2010-07-28 at 01:38 +0200, Christian Stroetmann wrote:
>>>> At the 28.07.2010 00:00, Ben Chociej wrote:
>>>> Wouldn't this feature be useful for other file systems as well, so that
>>>> a more general and not an only Btrfs related solution is preferable?
>>> Would certainly nice to add this feature to all filesystem, but right
>>> now btrfs is the only fs which have multiple device support in itself.
>> Why does it even need multiple devices in the filesystem? All the
>> filesystem needs to know is the relative speed of regions of it's
>> block address space and to be provided allocation hints. everything
>> else is just movement of data. You could keep the speed information
>> in the device mapper table and add an interface for filesystems to
>> query it, and then you've got infrastructure that all filesystems
>> could hook into.
>> The tracking features dont' appear to have anything btrfs specific
>> in them, so t iseems wrong to implement it there just because you're
>> only looking at btrfs' method of tracking multiple block devices
>> and moving blocks....
> I agree hot data tracking could be done at vfs layer. The current hot
> data temperature calculation and indexing code is very self-contained,
> and could be reuse to other fs or move up to vfs. We could define a
> common interface to export to hot data tempreture out. The relocation
> eventually has to be filesystem specific. btrfs does cow and knows where
> is the data on/off SSD directly makes the relocation to and from very
> straightforward.

Thanks for your thumb up. But maybe other interested persons should also
point their thumbs up at first before investing the effort of its
implementation. I mentioned this feature, because it is a trend that got
momentum in the area of (storage) virtualization and in this way in the
fields of cloud computing and service computing as well.

And: My both thumbs are already up. :D

> Mingming

Christian *<:o) O>-< -(D)>-<
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