Re: [RFC PATCH 0/5] Btrfs: Add hot data tracking functionality

From: Christian Stroetmann <stroetmann@ontolinux.com>
To: Mingming Cao <cmm@us.ibm.com>
Cc: Ben Chociej <bchociej@gmail.com>,
	Dave Chinner <david@fromorbit.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC PATCH 0/5] Btrfs: Add hot data tracking functionality
Date: Wed, 04 Aug 2010 20:44:02 +0200	[thread overview]
Message-ID: <4C59B4F2.5050404@ontolinux.com> (raw)
In-Reply-To: <1280943620.4676.65.camel@mingming-laptop>

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)>-<