(Optional) Plan disks|V4.6.0|OceanBase Database| docs|Distributed Database

(Optional) Plan disks

Last Updated：2026-07-23 10:04:28 Updated

The server of OceanBase Database depends on data disks, transaction log disks, and the installation disk of OceanBase Database. For personal trial scenarios, you can place all data on one disk and skip this step. For production environments, it is recommended to mount data to three separate disks.

If your machine does not have three disks, or if you are using a RAID disk array, you need to partition the disks or the logical volumes of the disk array. It is recommended that you use the following partitioning scheme:

Data disk

The data disk is used to store baseline data. The path is specified by the configuration parameter data_dir. When you first start an OceanBase cluster, ${data_dir}/{sstable,slog} will be automatically created. The size of the data disk is determined by the datafile_disk_percentage/datafile_size parameters. You can also perform dynamic expansion of disk files after deployment is complete using the datafile_next and datafile_maxsize configuration items. For more details, see Configure dynamic expansion of disk data files.

Note

The current version of OceanBase Database supports separating slog from the data disk. That is, slog and data files do not need to be on the same disk. For more information about the installation directory of OceanBase Database, see OBServer node installation directory structure.
Transaction log disk

The path of the transaction log disk is specified by the configuration parameter clog_dir. It is recommended to set the size of the transaction log disk to 3 to 4 times or more of the memory of OceanBase Database. When you first start an OceanBase cluster, ${clog_dir} will be automatically created. The transaction log disk contains multiple fixed-size files, and you can automatically create and clear transaction logs as needed. Automatic clearing is triggered when transaction logs reach 80% of the total disk capacity. However, transaction logs can only be deleted after the memory data corresponding to those logs has been merged into the baseline data.

For the same amount of data, the size of transaction logs is approximately three times the size of memory data. Therefore, the upper limit of space required for the transaction log disk is proportional to the total data volume after two major compactions. Empirical formula: Transaction log file size = 3 to 4 times the upper limit of incremental data memory.
OceanBase Database installation disk

The path of the OceanBase Database installation disk is specified by the configuration parameter home_path. It is recommended to reserve at least 200 GB of space for the OceanBase Database installation disk to store logs for 7 days or more. The installation directory of the OceanBase Database RPM package is located under ${home_path}. Here, baseline data files and transaction log files are linked via soft links to the independent data disk and transaction log disk, respectively. The operation logs of OceanBase Database are located under ${home_path}/log. Operation logs continue to grow, and OceanBase Database cannot delete them automatically, so you need to delete them periodically.

Disk mounting

Mounting requirements

The disk mount points for the OCP server are specified in the following table.

Mount point	Size	Purpose	File system format
/home	100 GB to 300 GB	Disk for component runtime logs	ext4 or xfs recommended
/data/log1	3 to 4 times the memory size allocated to observer	Disk for OCP MetaDB logs	ext4 or xfs recommended
/data/1	Depends on the amount of data to be stored	Disk for OCP MetaDB data	ext4 or xfs recommended

The disk mount points for the OBServer node are specified in the following table.

Directory	Size	Purpose	File system format
/home	100 GB to 300 GB	Disk for observer database installation	ext4 or xfs recommended
/data/log1	3 to 4 times the memory size allocated to observer	Disk for observer process logs	ext4 or xfs recommended
/data/1	Depends on the amount of data to be stored	Disk for observer process data	ext4 or xfs recommended

Note

We recommend that you set the root directory size to at least 50 GB. If you use LVM, we recommend that you create it with the striped parameter. Example:lvcreate -n data -L 3000G obvg --stripes=3 --stripesize=128.
We recommend that you use different disks for the data disk, log disk, and installation disk in a production environment to avoid performance issues.

Mounting procedure

Disk mounting must be performed as the root user. You can choose one of the following two methods based on your actual situation:

Use LVM tools to mount disks (recommended).
Use the fdisk tool to mount disks.

Use LVM tools to mount disks

Use the fdisk tool to mount disks.

View disk information

Run the fdisk -l command to identify available disks and partitions, and confirm the target device (for example, /dev/sdb1).
```
[root@test001 ~]# fdisk -l
```
(Optional) Install LVM tools

If LVM is not pre-installed, run the following command to install it. If LVM is already installed, skip this step.
- For Debian/Ubuntu systems
```
[root@test001 ~]# apt-get install lvm2
```
- CentOS/RHEL systems
```
[root@test001 ~]# yum install lvm2
```
Create a physical volume (PV)

Initialize the partition as a physical volume.

Notice

Initializing a partition as a physical volume will reformat the partition (data will be lost). Proceed with caution.
```
[root@test001 ~]# pvcreate /dev/sdb1
```
After creation, you can run the pvs command to verify the physical volume creation result.
Create a volume group (VG)

Combine multiple physical volumes into one VG.
```
[root@test001 ~]# vgcreate vg01 /dev/sdb1 /dev/sdc1 
```
After combination, you can run the vgs command to view the volume group information.
Create a logical volume (LV)

Allocate 100 GB of logical volume space from the VG. This is just an example; you can set the logical volume size according to your actual needs.
```
[root@test001 ~]# lvcreate -L 100G -n lv01 vg01
```
After creation, you can run the lvs command to view the logical volume information.

Format and mount

Format as an ext4 file system

[root@test001 ~]# mkfs.ext4 /dev/vg01/lv01

Create a mount point
```
[root@test001 ~]# mkdir -p /data/1
```

Temporarily mount

[root@test001 ~]# mount /dev/vg01/lv01 /data/1

Set up automatic boot-time mounting

Edit the /etc/fstab file and add the following mount configuration:
```
[root@test001 ~]# vim /etc/fstab
```
Add the following line to the /etc/fstab file:
```
/dev/vg01/lv01  /data/1  ext4  defaults,noatime,nodiratime,nodelalloc,barrier=0  0  0
```

Check disk information

Run the fdisk -l command to identify available disks and partitions, and confirm the target device (for example, /dev/sdb1).
```
[root@test001 ~]# fdisk -l
```
Create a partition

Use the fdisk tool to create a new partition. For example, run fdisk /dev/sdb1, enter n to create a primary partition, and then save the changes (w).
```
[root@test001 ~]# fdisk /dev/sdb1
```

Format and mount

Format the disk as an ext4 filesystem.
```
[root@test001 ~]# mkfs.ext4 /dev/sdb1
```
Create a mount point.
```
[root@test001 ~]# mkdir -p /data/1
```

Perform a temporary mount.

[root@test001 ~]# mount /dev/sdb1 /data/1

Set up automatic boot-time mounting.

Edit the /etc/fstab file and add the following mount configuration:
```
[root@test001 ~]# vim /etc/fstab
```
Add the following line to the /etc/fstab file:
```
/dev/sdb1  /data/1  ext4  defaults,noatime,nodiratime,nodelalloc,barrier=0  0  0
```

Check disks

After disks are mounted, you can run the following command to check the disk partitioning:

[root@test001 ~]# df -h

The return result is as follows:

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/sdb1     984G    77M  934G  1%  /data/1
/dev/vdc1     196G     61M   186G  1%  /data/log1
/dev/vdb1     492G    73M   467G  1%  /home/admin/oceanbase

The result description is as follows:

/data/1 is the data disk with a size of 1 TB.
/data/log1 stores logs.
/home/admin/oceanbase stores the binary files and runtime logs of OceanBase Database.

Ensure that the disks corresponding to data_dir, redo_dir, and home_path in the configuration file have been mounted. The directories corresponding to data_dir and redo_dir should be empty, and the disk usage of the directory corresponding to data_dir must be less than 4%.

Set directory permissions

After disks are mounted, you need to check the permissions of the directories where the disks are mounted. You can run the following command to view the permissions of the cluster-related file directories.

Here is an example using the data directory:

[root@test001 data]# ls -al

The return result is as follows, indicating that the directory owner is the admin user of the admin group:

drwxr-xr-x 2 admin admin 4096 Feb 9 18:43 .
drwxr-xr-x 2 admin admin 4096 Feb 9 18:43 log1

If you find that the admin user does not have the necessary permissions for the related files after checking the directory permissions, you can run the following command to change the file owner:

[root@test001 ~]# chown -R admin:admin /data/log1
[root@test001 ~]# chown -R admin:admin /data

Here, /data/log1 and /data are example mount directories. You need to replace them with your actual mount directories.

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(Optional) Plan disks

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Disk mounting

Mounting requirements

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Mounting procedure

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Check disks

Set directory permissions