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I always read that the outer edge of disk is the fastest place. Somebody said "You better put your Oracle Redo Log file at the outer edge of disk". My question is:

  1. How to put Redo Log file at specific location in disk?
  2. How much performance will it will increase?

By the way I'm using solaris 10 for Oracle 11g Database

Updated:

Here is the information about my disk

/dev/dsk/c0t1d0s0 is currently mounted on /oracle/diag
/dev/dsk/c0t1d0s1 is currently mounted on /oracle/oradata01
/dev/dsk/c0t1d0s3 is currently mounted on /oracle/oraredo01
/dev/dsk/c0t1d0s4 is currently mounted on /oracle/oraredo02
/dev/dsk/c0t1d0s5 is currently mounted on /oracle/fast_recovery_area
/dev/dsk/c0t1d0s6 is currently mounted on /oracle/backup
/dev/dsk/c0t1d0s7 is currently mounted on /oracle/data

Virtual Drive: 1 (Target Id: 1)
Name        :
RAID Level  : Primary-1, Secondary-0, RAID Level Qualifier-0
Size        : 835.394 GB
Mirror Data : 835.394 GB
State       : Optimal
Strip Size      : 64 KB
Number Of Drives per span:2
Span Depth  : 3
Default Cache Policy    : WriteBack, ReadAheadNone, Cached, No Write Cache if Bad BBU
Current Cache Policy    : WriteBack, ReadAheadNone, Cached, No Write Cache if Bad BBU
Access Policy   : Read/Write
Disk Cache Policy   : Disk's Default
Encryption Type         : None
Hajime
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2 Answers2

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Oracle redo files are written in a sequential fashion. This is what gives the best performance because the write head is always on the correct location to write again, as long as the disk is not shared with other files. As soon as the disk - or more precisely - the write head is shared with a datafile, the head has to make more movements to satisfy the random IO pattern that is mostly found for datafiles.

The cylinders numbering of disks start at the outer edge of the disk. See Oracle Solaris 11 System Administration: Administering Storage Devices for some info. While formatting the slices you can point them their location on disk.

If you really want high performant redo files, give them their own dedicated disks and stripe them for best performance. Don't forget that the archiver is also going to read the redo after it has been completed ....

Managing files on separate disks is something of the past. Since years Oracle preaches SAME. Stripe And Mirror Everything. See Optimals Storage Configuration Made Easy Add the disks to an ASM diskgroup and let ASM handle the file placement.

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The "outer edge of the disk" is advice from the 1980s. Before RAID. Before everyone had a caching disk controller. Ignore it.

If writing the redo logs is what is slowing your system down, move them to a faster disk or storage device. Your system is caching writes to the partitions mounted as /oracle/oraredo0{1,2}. Those partitions are competing for cache space and write time with all the other partitions on the c0t1d0 disk.

Scott Leadley
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