From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Hills Subject: Re: SSD cache with regular partition, like BSD swapcache Date: Fri, 16 Aug 2013 18:41:14 +0100 (BST) Message-ID: References: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: In-Reply-To: Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Adam Brenner Cc: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-bcache@vger.kernel.org On Thu, 15 Aug 2013, Adam Brenner wrote: > > Hence, looking for a non-writeback SSD cache which can be transparently > > added and removed from the system. > > Removing / Adding a caching device within Bcache can be done on a live > system, so long as a backing device is created before hand. This was > explained here: > http://comments.gmane.org/gmane.linux.kernel.bcache.devel/1886 Sorry, maybe I should have been more clear. I meant adding without modifying the _backing_ device. > > Doesn't look like it's possible from the docs; has there been any work on > > this -- a different 'glue' or front end? > > Is this what you are looking for? https://github.com/g2p/blocks > > This should keep any data on the backing device without the need to format. Not really, keeping the data on the partition is only part of the solution -- and this requires free space before the partiion, or LVM. As I said, I don't wish to modify the backing device at all (even in-place for risk to data) or use a new partition format (also prevents mounting the filesystem on other systems, or boot disks) And it's just not necessary anyway if using a non-persistent read cache. The nature of swapcache's integration makes it easier and less disruptive to configure -- especially for people who don't already use an initrd. It would make it easier to experiement with the caching in different scenarios. Thanks -- Mark