From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Merillat Subject: Re: bcache fails after reboot if discard is enabled Date: Wed, 8 Apr 2015 18:02:23 -0400 Message-ID: References: <54A66945.6030403@profihost.ag> <54A66C44.6070505@profihost.ag> <54A819A0.9010501@rolffokkens.nl> <54A843BC.608@profihost.ag> <55257303.8020008@profihost.ag> <3ldgvb-het.ln1@hurikhan77.spdns.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-ie0-f170.google.com ([209.85.223.170]:34348 "EHLO mail-ie0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754229AbbDHWCY (ORCPT ); Wed, 8 Apr 2015 18:02:24 -0400 Received: by iedfl3 with SMTP id fl3so97451933ied.1 for ; Wed, 08 Apr 2015 15:02:24 -0700 (PDT) In-Reply-To: <3ldgvb-het.ln1@hurikhan77.spdns.de> Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: Kai Krakow Cc: linux-bcache@vger.kernel.org You can't always use the correct eraseblock size with BCache, since it doesn't (didn't, at least at the time I created my cache) support non-powers-of-two that TLC drives use. That said, TRIM is not supposed to blow away entire eraseblocks, just let the drive know the mapping between presented LBA and internal address is no longer needed, allowing it to do what it wishes with that knowledge (generally reclaim multiple partial blocks to create fully empty blocks). I can't find any reports of errors with TRIM support in the 840-EVO series. They had/may still have a problem reading old data that was a big deal in the fall, and there was an 850 firmware that bricked some drives. Nothing about TRIM erasing unintended data, though. There were no problems with bcache at all in the year+ I've used it, until I enabled bcache discard. Before that, I put on over 100 terabytes of writes to the bcache partition with no interface errors. I've also never seen a TRIM failure in other filesystems using the same model in my other systems. There was no powerloss, the system went through a software reboot cycle before the failure. I'm therefore *extremely* hesitant about allowing this to be written off as a hardware failure.