The following is part of a series on the different aspects of disk I/O performance and optimization for Oracle...
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databases. Each tip is excerpted from the not-yet-released Rampant TechPress book, "Oracle disk I/O tuning," by Mike Ault. Check back to the main series page for upcoming installments.
As noted above, the -m sectcount and -u 1 options should be used with caution at first, preferably on a read-only file system. Most drives work well with these features, but a few drive/controller combinations are not 100% compatible. File system corruption may result. Backup everything before experimenting!
Some options (e.g. -r for SCSI) may not work with old kernels as necessary ioctl()'s were not supported.
Although this utility is intended primarily for use with (E) IDE hard disk devices, several of the options are also valid (and permitted) for use with SCSI hard disk devices and MFM/RLL hard disks with XT interfaces.
(The above list of parameters and notes derived from the Linux man (manual) pages)
As you can see, we can alter or control about every aspect of the ATA/IDE drive environment and report on some aspects (-r for read only status and -g for geometry, as well as the -T and -t testing parameters) of the SCSI environment on Linux using the hdparm command.
Let's go through an example disk tuning on a LINUX server using hdparm.
We have just installed a brand new 40 GB EIDE disk drive into our Linux server (aultlinux2.) Knowing about the hdparm command, we run it against the disk after we have configured it for use:
[root@aultlinux2 root]# hdparm /dev/hdb /dev/hdb: multcount = 16 (on) IO_support = 0 (default 16-bit) unmaskirq = 0 (off) using_dma = 0 (off) keepsettings = 0 (off) readonly = 0 (off) readahead = 8 (on) geometry = 77557/16/63, sectors = 78177792, start = 0
[root@aultlinux2 root]# hdparm -Tt /dev/hdb /dev/hdb: Timing buffer-cache reads: 128 MB in 1.63 seconds = 78.53 MB/sec Timing buffered disk reads: 64 MB in 14.20 seconds = 4.51 MB/sec
[root@aultlinux2 root]# hdparm -c1 -u0 -p -d0 /dev/hdb /dev/hdb: attempting to set PIO mode to 0 setting 32-bit IO_support flag to 1 setting unmaskirq to 0 (off) setting using_dma to 0 (off) IO_support = 1 (32-bit) unmaskirq = 0 (off) using_dma = 0 (off) [root@aultlinux2 root]# hdparm -Tt /dev/hdb /dev/hdb: Timing buffer-cache reads: 128 MB in 1.63 seconds = 78.53 MB/sec Timing buffered disk reads: 64 MB in 9.80 seconds = 6.53 MB/sec
[root@aultlinux2 root]# hdparm -m16 -c3 -X mdma2 -d1 -a8 -u1 /dev/hdb /dev/hdb: setting fs readahead to 8 setting 32-bit IO_support flag to 3 setting multcount to 16 setting unmaskirq to 1 (on) setting using_dma to 1 (on) setting xfermode to 34 (multiword DMA mode2) multcount = 16 (on) IO_support = 3 (32-bit w/sync) unmaskirq = 1 (on) using_dma = 1 (on) readahead = 8 (on) [root@aultlinux2 root]# hdparm -Tt /dev/hdb /dev/hdb: Timing buffer-cache reads: 128 MB in 1.56 seconds = 82.05 MB/sec Timing buffered disk reads: 64 MB in 4.29 seconds = 14.92 MB/sec
You will need to add the settings to your startup scripts (usually put it in the database start or Oracle kernel configuration script you use) since they will not be retained between reboots. In addition, you should add the -K flag to retain the settings between soft resets of the drive.
Even if you are only using the ATA drives for system software and swap area, you can see where tuning them using hdparm can make a significant performance difference for your system.
Click to buy the book, "Oracle disk I/O tuning," by Mike Ault.
About the author
Mike Ault is a SearchOracle.com expert and a senior Oracle consultant with Burleson Consulting, and one of the leading names in Oracle technology. The author of more than 20 Oracle books and hundreds of articles in national publications, Mike Ault has five Oracle Masters Certificates and was the first popular Oracle author with his landmark book "Oracle7 administration and management." Mike also wrote several of the "Exam Cram" books, and enjoys a reputation as a leading author and Oracle consultant. Ask Mike a question today!