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

From: Tracy Reed
Date: Tue Jul 27 2010 - 18:50:55 EST

On Tue, Jul 27, 2010 at 05:00:18PM -0500, bchociej@xxxxxxxxx spake thusly:
> The long-term goal of these patches, as discussed in the Motivation
> section at the end of this message, is to enable Btrfs to perform
> automagic relocation of hot data to fast media like SSD. This goal has
> been motivated by the Project Ideas page on the Btrfs wiki.

With disks being so highly virtualized away these days is there any
way for btrfs to know which are the fast outer-tracks vs the slower
inner-tracks of a physical disk? If so not only could this benefit SSD
owners but it could also benefit the many more spinning platters out
there. If not (which wouldn't be surprising) then disregard. Even just
having that sort of functionality for SSD would be excellent. If I
understand correctly not only would this work for SSD but if I have a
SAN full of many large 7200rpm disks and a few 15k SAS disks I could
effectively utilize that disk by allowing btrfs to place hot data on
the 15k SAS. I understand Compellent does this as well.

Tracy Reed

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