(Optional) Perform disk planning

The running of an OBServer node relies on the data disk, clog disk, and installation disk where OceanBase Database is installed. If you are an individual user, you can put all the data on a single disk and skip this topic. If you are an enterprise user, you must separately mount your data to three disks.

If you do not have three disks for a server, or if you are using Redundant Array of Independent Disks (RAID), you need to partition the disk or disk array into logical volumes. The recommended partitioning method is as follows:

• Data disk

  The data disk is used to store baseline data, and its path is specified by the data_dir parameter. When you start the OceanBase cluster for the first time, ${data_dir}/{sstable,slog} will be created automatically. The size of the data disk is determined by parameters datafile_disk_percentage and datafile_size. Additionally, after deployment, you can perform dynamic expansion of disk files through the datafile_next and datafile_maxsize options. For more information, see Configure automatic scale-out of disk space for data files.

• Clog disk

  The path of the clog disk is specified by the clog_dir parameter. We recommend that you set the size of the clog disk to 3 to 4 times or more of the memory for OceanBase Database. When you start the OceanBase cluster for the first time, ${clog_dir} will be created automatically. The clog disk contains multiple fixed-size files, which can be automatically created and cleared based on your needs. Automatic clearance is triggered when the clog reaches 80% of the total disk capacity. However, the clog can only be deleted when the corresponding memory data has been merged into the baseline data.

  For a given size of memory data, the size of clog files is approximately three times larger. Therefore, the maximum space required for the clog disk is directly proportional to the total amount of data after two major compactions. You can use the empirical formula for evaluation: Size of clog files = Maximum memory space for incremental data × 3 or 4.

• OceanBase Database installation disk

  The path of the installation disk is specified by the home_path parameter. We recommend that you reserve at least 200 GB to save log files for 7 or more days. The RPM package of OceanBase Database is located in the ${home_path} directory. The baseline data files and clog files are mapped to the preceding data disk and clog disk through soft links. The operational logs of OceanBase Database are located in the ${home_path}/log directory. The number of operational logs will keep increasing because OceanBase Database cannot automatically delete them. Therefore, you need to regularly delete the operational logs.

After you plan the disks, run the following command to view the disk information:

df -h

For example, the following output is returned:

Filesystem      Size  Used Avail Use% Mounted on
devtmpfs         31G     0   31G   0% /dev
tmpfs            31G     0   31G   0% /dev/shm
tmpfs            31G  516K   31G   1% /run
tmpfs            31G     0   31G   0% /sys/fs/cgroup
/dev/vda1       493G  171G  302G  37% /
tmpfs           6.2G     0  6.2G   0% /run/user/0
/dev/vdd1     984G    77M  934G  1%  /data
/dev/vdc1     196G     61M   186G  1%  /redo
/dev/vdb1     492G    73M   467G  1%  /home/admin/oceanbase

In the previous output:

• The /data string indicates the information of the data disk, which is 1 TB in size.

• The /redo string indicates the information of the log disk where the redo logs are stored.

• The /home/admin/oceanbase string indicates the information of the installation disk where the binary files and operational logs of OceanBase Database are stored.