Messages in this thread | | | Date | Thu, 29 Jul 2010 15:17:13 +0200 | From | Christian Stroetmann <> | Subject | Re: [RFC PATCH 0/5] Btrfs: Add hot data tracking functionality |
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Aloha Mingming, Aloha Dave;
On the 29.07.2010 14:17, 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. >> >
Thanks for your explanation, Mingming. And I had further questions to this point, but didn't know exactly how to formulate them in a short way. But luckily Dave has a possible solution that is related with my questions around the multiple device feature of Btrfs and hot data handling.
> Why does it even need multiple devices in the filesystem?
Yes, that was the point I asked myself after reading about this in the Btrfs wiki (https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices) and how ZFS does it.
> 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. >
Yes indeed, something like this general solution that doesn't need the multiple device feature at all.
> 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.... > > Cheers, > > Dave. >
Thank you very much for being creative. :D
Cheerio Christian *<:o) O>-< -(D)>-<
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