From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Mamedov Subject: Re: RAID creation resync behaviors Date: Thu, 4 May 2017 13:06:27 +0500 Message-ID: <20170504130627.4f20f79c@natsu> References: <20170503202748.7r243wj5h4polt6y@kernel.org> <20170503235856.GA9698@metamorpher.de> <20170504022258.eov6xh2zwtbfvcch@kernel.org> <20170504075551.GA3929@metamorpher.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170504075551.GA3929@metamorpher.de> Sender: linux-raid-owner@vger.kernel.org To: Andreas Klauer Cc: Shaohua Li , linux-raid@vger.kernel.org, jes.sorensen@gmail.com, neilb@suse.de List-Id: linux-raid.ids On Thu, 4 May 2017 09:55:51 +0200 Andreas Klauer wrote: > For example? I was under the impression that pretty much all of them do. > Even the ones that don't advertize it returned zero after trim for me. > [Sometimes you get original data but that's Linux; gone after drop_caches] > (Of course, I don't have access to that many different models of SSD...) > > But what do they actually return then? Original data? Consult Wikipedia at least, if not the original ATA standards documents: https://en.wikipedia.org/wiki/Trim_(computing)#ATA Can return "undefined", "something that is the same every time" or "zeroes". Apparently the OS can query which is to be expected with a particular device, but firstly, you can't necessarily trust that 100%, and secondly, that's operating on a level lower (ATA) than where md is. -- With respect, Roman