Installation Guide > Installation Guide > Understanding Installation Considerations > File Location Guidelines > II_DATABASE (Database Files) Location Guidelines
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II_DATABASE (Database Files) Location Guidelines
The instance default data location contains the master database (iidbdb), which stores information about all databases, their locations, and the users that can access them. By default, this location also contains all user databases, unless the database administrator specifies an alternate location for a database when creating it.
When choosing the data location, consider the following:
• Place database files on a separate disk from checkpoint, journal, and dump files to maximize chances for data recovery.
• Place database files on a separate disk from the transaction log files to improve system performance by distributing disk I/O.
• Place database files on a separate disk from the work locations. Doing so prevents work operations that might fill the file system from having an impact on the data location, reduces fragmentation of both locations, and ensures sufficient reading bandwidth for the data location.
• On systems with three or more disks, do not place the database files on the same disk as your operating system. Administrators typically will want to improve reliability by avoiding a large amount of file create, open, and close activity on the operating system disk and not risk the operating system disk running out of space.
• Keep the usage of data file systems below 75 percent. Above this level, fragmentation will be more rapid and will degrade the efficiency of scanning operations. You will also need sufficient space to reorganize tables as part of database maintenance.
If you lose this location, Actian X will fail. You must replace the failed component, recreate the directory structure, and recover from checkpoint and journals all Actian X databases that use this location.
If you fill this file system, Actian X will fail. Free some space or allocate additional space, and restart Actian X if necessary.
The I/O bandwidth requirement for this file system depends on your reading and writing rates to the user databases using it (iidbdb requires almost none). Unless these are well-tuned OLTP databases, partial and complete scans of tables will dominate the reading. A larger Actian X cache will reduce reading, but will have almost no effect on substantial table scanning.
Warnings on Specific File and Storage Systems
IMPORTANT!  Warnings!
• We strongly recommend that you do not use ReiserFS for data locations due to severe performance degradation noticed when using this file system.
• We strongly recommend that you do not use a RAID5 storage configuration for data locations. Striping increases performance; redundancy increases data security. Economizing on disks does not typically pay in the long run.
• The ext4 file system on Red Hat Enterprise Linux 6 uses a default setting of barrier=1, which causes poor performance in Actian X. We recommend a setting of barrier=0. The barrier=0 setting, while safe for Actian X, may cause data corruption in other applications in the event of a crash. To understand the risks of disabling barriers, see the RHEL6 Storage Administration Guide (https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/pdf/Storage_Administration_Guide/Red_Hat_Enterprise_Linux-6-Storage_Administration_Guide-en-US.pdf).
Last modified date: 08/14/2024