From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gabriel de Perthuis Subject: Re: bcache & btrfs: "Btrfs detected SSD devices, enabling SSD mode" Date: Fri, 20 Sep 2013 18:25:24 +0200 Message-ID: <523C76F4.3070809@gmail.com> References: <523C71C4.9030606@rolffokkens.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <523C71C4.9030606-6w2rdlBuEQTpMFipWq+H6g@public.gmane.org> Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Rolf Fokkens Cc: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-bcache@vger.kernel.org > This may be known already, but I noticed the following message in sys= log > during boot: >=20 > Btrfs detected SSD devices, enabling SSD mode >=20 > Btrfs is right in a sense: there is a SSD involved, but there's a HDD= as > well. I don't think it is an issue, but I have no idea how "btrfs' SS= D > optimizations" will interact with bcache. Might be interesting. =46rom https://btrfs.wiki.kernel.org/ : > SSD [=85] optimizations (e.g. avoiding unnecessary seek optimizations= , sending writes in clusters, even if they are from unrelated files. This results in larger write operations and faster write throughput) The optimisations should be beneficial iff bcache is used in writeback mode. ssd_spread and discard are enabled separately; I'm not sure what ssd_spread (from the wiki: more strict about finding a large unused region of the disk for new allocations) would do for bcache.