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Log file space. Unlike executable and administrative space, the space configured for log files is critical to the overall performance and security of a database app. Each update or transaction to the database is logged or journaled through these files. I/O to the mount points housing these files is critical to overall database performance. The storage array, OS and database app must work in concert to maximize I/O to this space.

For example, disk groups within the array should have enough spindles to maximize I/O without causing unnecessary waits for a small piece of data to be written to 20 disks. For the log file space, create two RAID 1/0 disk groups that have approximately four physical disks with a stripe size of 64KB or greater. The disks should be striped and mirrored to provide high I/O and protection. After the space for the log and archive files is allocated from this volume group, the remaining space can be used for tablespace(s).

Database tablespace. The actual row/column information is stored in multiple files managed by the database and app. In our SAP/Oracle example, these are mount points /oracle/<SAPID>/sapdata1, /oracle/ <SAPID>/sapdata2 and so forth. Disk groups should be built from a minimum of six disks and be protected using RAID 5.

Once the physical disks have been grouped into appropriate disk groups and presented to the server, system admins can handle logical configuration, formatting

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and mounting the space to the file system. Because the array is providing RAID 1/0 and RAID 5 protection for the log file space and tablespace respectively, the system admin shouldn't mirror or stripe these logical volumes. While volume managers have this capability, the array capabilities can be leveraged to provide this type of protection. The system admin should format the file-system space with a block size that matches the write size of the database--an 8KB block size in most cases. Even with 32GB or 64GB disk groups, this block size should be adequate.

This was first published in December 2006

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