From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:47683 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752809AbcEQG1b (ORCPT ); Tue, 17 May 2016 02:27:31 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1b2YTU-0001yC-29 for linux-btrfs@vger.kernel.org; Tue, 17 May 2016 08:27:24 +0200 Received: from 145.132.48.198 ([145.132.48.198]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 17 May 2016 08:27:24 +0200 Received: from ftoth by 145.132.48.198 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 17 May 2016 08:27:24 +0200 To: linux-btrfs@vger.kernel.org From: Ferry Toth Subject: Re: Hot data tracking / hybrid storage Date: Tue, 17 May 2016 06:27:14 +0000 (UTC) Message-ID: References: <20160516010524.7e208f96@jupiter.sol.kaishome.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Op Mon, 16 May 2016 01:05:24 +0200, schreef Kai Krakow: > Am Sun, 15 May 2016 21:11:11 +0000 (UTC) > schrieb Duncan <1i5t5.duncan@cox.net>: > >> Ferry Toth posted on Sun, 15 May 2016 12:12:09 +0000 as excerpted: >> > > You can go there with only one additional HDD as temporary storage. Just > connect it, format as bcache, then do a "btrfs dev replace". Now wipe > that "free" HDD (use wipefs), format as bcache, then... well, you get > the point. At the last step, remove the remaining HDD. Now add your > SSDs, format as caching device, and attach each individual HDD backing > bcache to each SSD caching bcache. > > Devices don't need to be formatted and created at the same time. I'd > also recommend to add all SSDs only in the last step to not wear them > early with writes during device replacement. > > If you want, you can add one additional step to get the temporary hard > disk back. But why not simply replace the oldest hard disk with the > newest. Take a look at smartctl to see which is the best candidate. > > I went a similar route but without one extra HDD. I had three HDDs in > mraid1/draid0 and enough spare space. I just removed one HDD, prepared > it for bcache, then added it back and removed the next. > That's what I mean, a lot of work. And it's still a cache, with unnecessary copying from the ssd to the hdd. And what happens when either a hdd or ssd starts failing? > -- > Regards, > Kai > > Replies to list-only preferred.