Monitoring ASM disk performance using IOSTAT
April 18, 2022 Leave a comment
iostat in asmcmd displays I/O statistics for Oracle ASM disks in mounted disk groups.
Connect to the database node via GI owner:
# su - grid
Run iostat with the following options (Reads & Writes are in bytes):
# asmcmd ASMCMD> iostat -t -G FRA 5 Group_Name Dsk_Name Reads Writes Read_Time Write_Time FRA RAC1$LUN3 585083392 98942464 94.659862 4.03044 FRA RAC2$LUN3 1847296 98942464 .054822 4.134049 FRA RACQ$LUN4 57344 24576 .035944 .018594 Group_Name Dsk_Name Reads Writes Read_Time Write_Time FRA RAC1$LUN3 368640.00 0.00 0.01 0.00 FRA RAC2$LUN3 0.00 0.00 0.00 0.00 FRA RACQ$LUN4 0.00 0.00 0.00 0.00
Where -t displays time statistics (Read_Time, Write_Time)-G FRA displays statistics for the FRA diskgroup, change the diskgroup name according to your needs. 5 is a refresh interval. When the interval is specified then the value displayed (bytes or I/Os) is the difference between the previous and current values, not the total value. But if a refresh interval is not specified, the number displayed represents the total number of bytes or I/Os.
For synopsis and description about all available iostat options, run help:
ASMCMD> help iostat
iostat
Displays I/O statistics for Oracle ASM disks in mounted disk groups.
Synopsis
iostat [-et][--io] [--suppressheader] [--region] [-G <diskgroup>] [<interval>]
Description
iostat lists disk group statistics using the V$ASM_DISK_STAT view.
The options for the iostat command are described below.
-e - Displays error statistics (Read_Err, Write_Err).
-G diskgroup - Displays statistics for the disk group name.
--suppressheader - Suppresses column headings.
--io - Displays information in number of I/Os, instead
of bytes.
-t - Displays time statistics (Read_Time, Write_Time).
--region - Displays information for cold and hot disk regions
(Cold_Reads, Cold_Writes, Hot_Reads, Hot_Writes).
interval - Refreshes the statistics display based on the
interval value (seconds).
The attribute descriptions for iostat command output are described
below. To view the complete set of statistics for a disk group,
use the V$ASM_DISK_STAT view.
Group_Name Name of the disk group.
Dsk_Name Name of the disk.
Reads Total number of bytes read from the disk.
If the --io option is entered, then the value
is displayed as number of I/Os.
Writes Total number of bytes written to the disk.
If the --io option is entered, then the value
is displayed as number of I/Os.
Cold_Reads Total number of bytes read from the cold disk
region. If the --io option is entered, then
the value is displayed as number of I/Os.
Writes Total number of bytes written to the disk.
Cold_Writes Total number of bytes written to the cold
disk region. If the --io option is entered,
then the value is displayed as number of I/Os.
Hot_Reads Total number of bytes read from the hot
disk region. If the --io option is entered,
then the value is displayed as number of I/Os.
Writes Total number of bytes written to the disk.
Cold_Writes Total number of bytes written to the cold
Hot_Writes Total number of bytes written to the hot disk
region. If the --io option is entered, then the
value is displayed as number of I/Os.
Read_Err Total number of failed I/O read requests for
the disk.
Write_Err Total number of failed I/O write requests for
the disk.
Read_Time Total I/O time (in seconds) for
read requests for the disk if the
TIMED_STATISTICS initialization parameter is
set to TRUE (0 if set to FALSE).
Write_Time Total I/O time (in seconds) for
write requests for the disk if the
TIMED_STATISTICS initialization parameter is
set to TRUE (0 if set to FALSE).
Writes Total number of bytes written to the disk.
Cold_Writes Total number of bytes written to the cold
Hot_Writes Total number of bytes written to the hot disk
If a refresh interval is not specified, the number displayed represents
the total number of bytes or I/Os. Ifa refresh interval is specified,
then the value displayed (bytes or I/Os) is the difference between the
previous and current values, not the total value.
Examples
The following are examples of the iostat command. The first example
displays disk I/O statistics for the data disk group in total number
of bytes. The second example displays disk I/O statistics for the data
disk group in total number of I/O operations.
ASMCMD [+] > iostat -G data
Group_Name Dsk_Name Reads Writes
DATA DATA_0000 180488192 473707520
DATA DATA_0001 1089585152 469538816
DATA DATA_0002 191648256 489570304
DATA DATA_0003 175724032 424845824
DATA DATA_0004 183421952 781429248
DATA DATA_0005 1102540800 855269888
DATA DATA_0006 171290624 447662592
DATA DATA_0007 172281856 361337344
DATA DATA_0008 173225472 390840320
DATA DATA_0009 288497152 838680576
DATA DATA_0010 196657152 375764480
DATA DATA_0011 436420096 356003840
ASMCMD [+] > iostat --io -G data
Group_Name Dsk_Name Reads Writes
DATA DATA_0000 2801 34918
DATA DATA_0001 58301 35700
DATA DATA_0002 3320 36345
DATA DATA_0003 2816 10629
DATA DATA_0004 2883 34850
DATA DATA_0005 59306 38097
DATA DATA_0006 2151 10129
DATA DATA_0007 2686 10376
DATA DATA_0008 2105 8955
DATA DATA_0009 9121 36713
DATA DATA_0010 3557 8596
DATA DATA_0011 17458 9269
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