From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: Some very basic questions Date: Tue, 21 Oct 2008 13:15:13 -0400 Message-ID: <20081021171513.GA8799@infradead.org> References: <20081021132322.271ad728.skraw@ithnet.com> <48FDD710.5050702@hp.com> <20081021190136.89b2c6af.skraw@ithnet.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: jim owens , linux-btrfs@vger.kernel.org To: Stephan von Krawczynski Return-path: In-Reply-To: <20081021190136.89b2c6af.skraw@ithnet.com> List-ID: On Tue, Oct 21, 2008 at 07:01:36PM +0200, Stephan von Krawczynski wrote: > Sure, but what you say only reflects the ideal world. On a file service, you > never have that. In fact you do not even have good control about what is going > on. Lets say you have a setup that creates, reads and deletes files 24h a day > from numerous clients. At two o'clock in the morning some hd decides to > partially die. Files get created on it, fill data up to errors, get > deleted and another bunch of data arrives and yet again fs tries to allocate > the same dead areas. You loose a lot more data only because the fs did not map > out the already known dead blocks. Of course you would replace the dead drive > later on, but in the meantime you have a lot of fun. > In other words: give me a tool to freeze the world right at the time the > errors show up, or map out dead blocks (only because it is a lot easier). When modern disks can't solve the problems with their internal driver remapping anymore you better replace it ASAP as it is a very strong disk failure indication. Last years FAST has some very interesting statitics showing this in the field.