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?
thanks
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LEARN ABOUT OPENSOLARIS
cfsetospeed
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)