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Operating Systems AIX LVM & Raw device i/o comparison Post 302579173 by royalliege on Monday 5th of December 2011 03:31:46 AM
Old 12-05-2011
LVM & Raw device i/o comparison

Please consider this a question about basics&best practices. On AIX 5.3 system, three raw physical volumes are defined from storage. While doing a read with command dd from the raw device, the speed rate is 250Mb/s.

Then, it gets complex when I define these three pv's to an lv of type raw. Doing a read from raw lv, the speed rate is 11Mb/s for each pv's giving a total of 33Mb/s.

I tried with different options sequential, parallel ...

Still no luck of getting closer to 250Mb/s. Is it reasonable or is there a best practice of getting closer to the speed rate with some parameters at the time of creating lv?

Smilie thanks
 

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cfsetispeed(3C) 					   Standard C Library Functions 					   cfsetispeed(3C)

NAME
cfsetispeed, cfsetospeed - set input and output baud rate SYNOPSIS
#include <termios.h> int cfsetispeed(struct termios *termios_p, speed_t speed); int cfsetospeed(struct termios *termios_p, speed_t speed); DESCRIPTION
The cfsetispeed() function sets the input baud rate stored in the structure pointed to by termios_p to speed. The cfsetospeed() function sets the output baud rate stored in the structure pointed to by termios_p to speed. There is no effect on the baud rates set in the hardware until a subsequent successful call to tcsetattr(3C) on the same termios structure. RETURN VALUES
Upon successful completion, cfsetispeed() and cfsetospeed() return 0. Otherwise -1 is returned, and errno may be set to indicate the error. ERRORS
The cfsetispeed() and cfsetospeed() functions may fail if: EINVAL The speed value is not a valid baud rate. EINVAL The value of speed is outside the range of possible speed values as specified in <termios.h>. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-------------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-------------------------------+ |Interface Stability |Standard | +-----------------------------+-------------------------------+ |MT-Level |MT-Safe, and Async-Signal-Safe | +-----------------------------+-------------------------------+ SEE ALSO
cfgetispeed(3C), tcsetattr(3C), attributes(5), standards(5), termio(7I) SunOS 5.11 24 Jul 2002 cfsetispeed(3C)
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