Block device to character device
Hi All, I have a situation here. One of my customer is configured their chunk on block device and character device. As data growth there it suffered with I/O bottleneck on some of the chunk. According to them those are block device chunk. So my questions are: 1. Is there a simple way to convert those block devices to character devices? 2. Is that true: block device is always slower then character devices? Since block device uses buffered I/O it still depend on UNIX read/write. While character device bypass the UNIX I/O, hence read/write would be faster. How true is this statement? Am i asking nonsense? :) Help is much appreciated. Thanks, Patrick
Hi, I have had this once, and we just set a link for the chunk dev to the corresponsing r* dev. Database down and up and that was it (because the devices have obviously the same content, there is no need to convert anything. And: yes, block devices may slow down your database server, because the OS is in between. Marcus -----Original Message----- From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of PATRICK LEY Sent: Monday, November 06, 2006 9:32 AM To: ids@iiug.org Subject: Block device to character device [7730] Hi All, I have a situation here. One of my customer is configured their chunk on block device and character device. As data growth there it suffered with I/O bottleneck on some of the chunk. According to them those are block device chunk. So my questions are: 1. Is there a simple way to convert those block devices to character devices? 2. Is that true: block device is always slower then character devices? Since block device uses buffered I/O it still depend on UNIX read/write. While character device bypass the UNIX I/O, hence read/write would be faster. How true is this statement? Am i asking nonsense? :) Help is much appreciated. Thanks, Patrick **************************************************************************** *** Forum Note: Use "Reply" to post a response in the discussion forum.
What version of IDS are you using? Normally helpful it's important to this question because the fix is easier in later releases. Yes, raw (character) devices tend to be 15-25% faster than the corresponding cooked (block) device. And yes there are ways to remap the chunks. Art S. Kagel ----- Original Message ----- From: Patrick Ley <ids@iiug.org> At: 11/06 3:40:23 Hi All, I have a situation here. One of my customer is configured their chunk on block device and character device. As data growth there it suffered with I/O bottleneck on some of the chunk. According to them those are block device chunk. So my questions are: 1. Is there a simple way to convert those block devices to character devices? 2. Is that true: block device is always slower then character devices? Since block device uses buffered I/O it still depend on UNIX read/write. While character device bypass the UNIX I/O, hence read/write would be faster. How true is this statement? Am i asking nonsense? :) Help is much appreciated. Thanks, Patrick ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.
Hi ART KAGEL, The version of informix is : IBM Informix Dynamic Server Version 9.30.FC6 and the OS is HP-UX metricap B.11.11 U 9000/800 3729261492 unlimited-user license Is there any convertion needed? Or as stated by Marcus Haarmann just broke the symbolic link and point it to the rvol? Help is much greatful. Thanks, Patrick.
OK, 9.30 does not support chunk renaming (9.40+ does), but since you had the foresight to use symlinks for your chunk paths you are living in a honey pot as my father-in-law was fond of saying. Yes, just repoint the links from the cooked(block) devices to the raw(character) devices and restart the instance. Voila! It's that simple. Done it a few times myself when someone added chunks before drinking coffee in the AM! Works like a charm. Art S. Kagel ----- Original Message ----- From: Patrick Ley <ids@iiug.org> At: 11/06 22:52:31 Hi ART KAGEL, The version of informix is : IBM Informix Dynamic Server Version 9.30.FC6 and the OS is HP-UX metricap B.11.11 U 9000/800 3729261492 unlimited-user license Is there any convertion needed? Or as stated by Marcus Haarmann just broke the symbolic link and point it to the rvol? Help is much greatful. Thanks, Patrick. ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.