From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ric Wheeler Subject: Re: impact of 4k sector size on the IO & FS stack Date: Sun, 11 Mar 2007 22:37:04 -0400 Message-ID: <45F4BCD0.3040601@emc.com> References: <45F48809.2060908@emc.com> <20070312000253.20eab1a3@lxorguk.ukuu.org.uk> <45F4A268.3000405@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Alan Cox , linux-scsi , linux-fsdevel@vger.kernel.org, Linux-ide To: Jeff Garzik Return-path: In-Reply-To: <45F4A268.3000405@garzik.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Jeff Garzik wrote: > Alan Cox wrote: >> I would be interested to know what the disk vendors intend to use as >> their strategy when (with ATA) they have a 512 byte write from an older >> file system/setup into a 4K block. The case where errors magically >> appear > > Well, you have logical and physical sector size changes. > > First generation of 1K sector drives will continue to use the same > 512-byte ATA sector size you are familiar with. A single 512-byte > write will cause the drive to perform a read-modify-write cycle. This > configuration is physical 1K sector, logical 512b sector. It would seem that most writes would avoid this - hopefully the drive firmware could use the write cache to coalesce contiguous IO's into 1k multiples when getting streams of 512 byte write requests. > > A future configuration will change the logical ATA interface away from > 512-byte sectors to 1K or 4K. Here, it is impossible to read a > quantity smaller than 1K or 4K, whatever the sector size is. > > Jeff I will try and see if I can get some specific information on when the various flavors of this are going to appear... ric