Introduction: Oracle Database supports multiple file system for hosting the Data files. Oracle ASM is the recommended storage solution from oracle for storing the data files. Oracle ASM Instance is supported in RAC and as well as in Non-RAC environments. There are many organizations who are not using the ASM as an storage solution due to their own reasons and still they are dependent on the third party file system. Oracle ZFS (Zeta Byte File System) is owned by Oracle and on all Solaris operating Environment ZFS is the only recommended option for managing the Storage devices. In Oracle Solaris 11 the default file system for "root" is also ZFS and we cannot use any other file system as an option for "root" file system. We can use UFS or any other third party file system for other mount-points/storage devices. In Solaris 10 operating environment there is choice to use ZFS/UFS file system for root and other mount-points/storage devices (HDD). In my observation all Oracle Solaris 11 operating Environments are using ZFS file system for managing all storage devices. ZFS is a robust file system and it has many excellent features like compression, multi size block support, snap clone etc. In this article we will see the recommended method of using ZFS file system for storing the Data files. Oracle Database Considerations for ZFS File System: Oracle ZFS file system will use 128K block size by default and Oracle uses default block size of 8K. Its been observed that customers using Oracle database on ZFS file system will use the default record size (128K) which is not recommended and it is against Oracle best practices. We have to make sure that we are using the same database block size as of ZFS record size. recordsize = db_block_size We can create ZFS file systems with different record sizes. This we will see in detail in the below demonstration. Demonstration: Lets see the generic database block size configuration on the solaris system on which all default parameters has been used. SQL> show parameter db_block_size NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ db_block_size integer 8192 SQL> select name, block_size from v$datafile; NAME BLOCK_SIZE -------------------------------------------------- ---------- /u01/oradata/PRODDB/system01.dbf 8192 /u01/oradata/PRODDB/rcat_ts01.dbf 8192 /u01/oradata/PRODDB/sysaux01.dbf 8192 /u01/oradata/PRODDB/undotbs01.dbf 8192 /u01/oradata/PRODDB/users01.dbf 8192 Lets see the OS block size of the respective database file system; root@solaris113:~# zfs get recordsize data_pool NAME PROPERTY VALUE SOURCE data_pool recordsize 128K default root@solaris113:~# The default block size of the operating system is 128K which is not correct as per the oracle documentation. The different block size at DB and OS level works pretty fine but this configuration may cause performance issues in the long run. So its higghly recommended to use the same block size at both database and OS level. Lets see how we can configure different block sizes for keeping different database files. Table below illustrates the recommended block sizes to be used for respective datafiles. Type of Files Oracle Block size Recommendation OLTP Datafiles 8K DSS Datafiles 16K/32K TEMP Files 128k/1M REDO,UNDO,Archive Logs 1M Now in this demonstration we will use two disks (LUNS) for storing OLTP/DSS and DB -LOG/UNDO/TEMP Files with different block sizes. root@solaris113:~# echo | format Searching for disks...done AVAILABLE DISK SELECTIONS: 0. c1t0d0 /pci@0,0/pci8086,2829@d/disk@0,0 1. c1t2d0 /pci@0,0/pci8086,2829@d/disk@2,0 2. c1t3d0 /pci@0,0/pci8086,2829@d/disk@3,0 3. c1t4d0 /pci@0,0/pci8086,2829@d/disk@4,0 Specify disk (enter its number): Specify disk (enter its number): root@solaris113:~# Disk3 - c1t3d0 will be used for OTLP/DSS datafiles Disk4 - c1t4d0 will be used for REDO,UNDO,Archive Logs - Creation of ZFS Data Pools We will create two ZFS pools "OLTP_DATA" and "LOG_DATA" root@solaris113:~# zpool create oltp_data c1t3d0 root@solaris113:~# zpool status oltp_data pool: oltp_data state: ONLINE scan: none requested config: NAME STATE READ WRITE CKSUM oltp_data ONLINE 0 0 0 c1t3d0 ONLINE 0 0 0 errors: No known data errors root@solaris113:~# root@solaris113:~# zpool create log_data c1t4d0 root@solaris113:~# zpool status log_data pool: log_data state: ONLINE scan: none requested config: NAME STATE READ WRITE CKSUM log_data ONLINE 0 0 0 c1t4d0 ONLINE 0 0 0 errors: No known data errors root@solaris113:~# Now check the block sizes of the respective pools. root@solaris113:~# zfs get recordsize oltp_data NAME PROPERTY VALUE SOURCE oltp_data recordsize 128K default root@solaris113:~# root@solaris113:~# zfs get recordsize log_data NAME PROPERTY VALUE SOURCE log_data recordsize 128K default root@solaris113:~# Creation of ZFS data sets with different block sizes: Create zfs data set with 8K size in "oltp_data": root@solaris113:~# zfs create -o recordsize=8k -o mountpoint=/dbdata/datafiles oltp_data/datafiles root@solaris113:~# zfs list | grep oltp oltp_data 132K 9.78G 31K /oltp_data oltp_data/datafiles 31K 9.78G 31K /dbdata/datafiles root@solaris113:~# zfs get recordsize oltp_data/datafiles NAME PROPERTY VALUE SOURCE oltp_data/datafiles recordsize 8K local root@solaris113:~# Similarly create the data set with "1M" size in "log_data": root@solaris113:~# zfs create -o recordsize=1m -o mountpoint=/logdata/redofiles log_data/redofiles root@solaris113:~# zfs create -o recordsize=1m -o mountpoint=/logdata/temp log_data/temp root@solaris113:~# zfs create -o recordsize=1m -o mountpoint=/logdata/undofiles log_data/undofiles root@solaris113:~# zfs list | grep logdata log_data/redofiles 31K 24.5G 31K /logdata/redofiles log_data/temp 31K 24.5G 31K /logdata/temp log_data/undofiles 31K 24.5G 31K /logdata/undofiles Get the record size for these data sets: root@solaris113:~# zfs get recordsize log_data/redofiles NAME PROPERTY VALUE SOURCE log_data/redofiles recordsize 1M local root@solaris113:~# zfs get recordsize log_data/temp NAME PROPERTY VALUE SOURCE log_data/temp recordsize 1M local root@solaris113:~# zfs get recordsize log_data/undofiles NAME PROPERTY VALUE SOURCE log_data/undofiles recordsize 1M local Creation of database with datafiles, logfiles, tempfiles on different location corresponding to the supported block sizes using dbca: - Click on customize locations in order to change the location of the datafiles, controlfiles and redo logfiles. By default datafiles are pointing to the "ORACLE_BASE" location, but we have to change the location of undo and tempfile to the data set of 1M size. - /logdata/undofiles and /logdata/temp data set are of 1M size. - Similarly we should change the location of the redo logfles. - Finally Ensure all database files are pointing to the correct data set block size with respect to the recommendation from the above table Verify the DB and OS block sizes after database creation: SQL> @db_structue.sql Control Files Location >>>> Control Files ------------------------------------------------------------ /dbdata/datafiles/TESTDB/control01.ctl /dbdata/datafiles/TESTDB/control02.ctl Redo Log File Locations >>>> GROUP# Online REDO Logs ---------- -------------------------------------------------- 3 /logdata/redofiles/TESTDB/redo03.log 2 /logdata/redofiles/TESTDB/redo02.log 1 /logdata/redofiles/TESTDB/redo01.log Data Files Locations >>>> ID Database Data Files MBYTE Sta TSPACE ----- -------------------------------------------------- ---------- --- ------------------------- 3 /dbdata/datafiles/TESTDB/sysaux01.dbf 670 OK SYSAUX 1 /dbdata/datafiles/TESTDB/system01.dbf 770 OK SYSTEM 4 /logdata/undofiles/TESTDB/undotbs01.dbf 55 OK UNDOTBS1 6 /dbdata/datafiles/TESTDB/users01.dbf 5 OK USERS ---------- Total 1500 SQL> We can verify the block sizes of all listd above data set using command " zfs get recordsize " Conclusion: Oracle highly recommends to match the ZFS record size to the Oracle_db_block_size for getting a better OLTP performance. Always its a best practice to keep the Redo logfiles, archive logfiles and tempfiles on a seperate data set which will help database with I/O overheads. For Redo logfiles, archive logfiles and tempfiles we should use the ZFS recordsize to the bigger value, in this artcile demonstration we used 1M which performs reasonably good. Its very simple to configure the ZFS recordsize for a Data Set, but in most of the customer environments I've seen this block sizing has not been considered at all, I would highly recommed to use the suggested block sizing to have a better performance on your database I/O.
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