From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christer Weinigel Subject: Re: Tuning for Compact Flash Date: Tue, 30 Sep 2008 01:11:49 +0200 Message-ID: <48E160B5.1090502@weinigel.se> References: <48DE2D20.1090703@csr.com> <48DFA291.2030206@hp.com> <48E0C8DA.6090502@weinigel.se> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: jim owens , linux-fsdevel@vger.kernel.org To: "Martin K. Petersen" Return-path: Received: from 2-1-3-15a.ens.sth.bostream.se ([82.182.31.214]:47098 "EHLO zoo.weinigel.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752304AbYI2XL4 (ORCPT ); Mon, 29 Sep 2008 19:11:56 -0400 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Martin K. Petersen wrote: >>>>>> "Christer" == Christer Weinigel writes: > > Christer> Of course it won't behave like a hard drive, but it would be > Christer> nice if there was a file system with performance that didn't > Christer> suck as badly on a compact flash. > > Well, you are limited by the capabilities of the FTL. And as far as > CF goes the FTL is usually pretty braindead. Yeah, I wish some flash manufacturer would do the right thing and just stick some NAND chips and some PCI/PCIe glue on a CardBus/ExpressCard. Something that allows a Linux driver to talk directly to the flash chips and then a simple DMA engine to do bus mastering block transfers to and from memory. We could then run yaffs or whatever we wanted on it with no translation layers at all in between. > But as far as CF is concerned I have tested many and not found a > single one that is suitable for a regular (random) filesystem write > workload. To the extent that for embedded devices I ended up putting > a root filesystem tarball on the CF and unpacking it into ramfs during > boot. > > And just to give you an idea: I'm getting two orders of magnitude less > random write ops on a (high-performance) CF than on a flash SSD from > the same vendor. In both cases with I/O aligned to the flash page > boundary. That sounds just horrid. Oh well, I won't have much choice when my hard drive dies, drives in this form factor are not manufactured any more and the only thing that will fit into the slot is a Compact Flash card or maybe with some hacking a USB drive. :-) /Christer