(Optional) Perform disk planning|V4.4.2| docs|Distributed Database

(Optional) Perform disk planning

Last Updated：2026-03-06 07:02:42 Updated

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, we recommend that you mount your data to three separate 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 parameters. For more information, see Configure automatic scale-out of disk space for data files.

Note

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

Disk mounting

Mounting requirements

Disk mount point requirements for OceanBase Cloud Platform (OCP) servers are shown in the following table.

Mount point	Size	Purpose	File system format
/home	100 GB~300 GB	Runtime log disk for components	ext4 or xfs recommended
/data/log1	3~4 times the memory allocated to observer	OCP metadata database log disk	ext4 or xfs recommended
/data/1	Depends on the required data storage size	OCP metadata database data disk	ext4 or xfs recommended

Disk mount point requirements for OBServer nodes are shown in the following table.

Directory	Size	Purpose	File system format
/home	100 GB~300 GB	observer database installation disk	ext4 or xfs recommended
/data/log1	3~4 times the memory allocated to observer	observer process log disk	ext4 or xfs recommended
/data/1	Depends on the required data storage size	observer process data disk	ext4 or xfs recommended

Note

We recommend that the root directory be at least 50 GB. If you use LVM, use striping parameters when creating. 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 production to avoid performance issues.

Mount operations

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

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

Use LVM tools to mount disks

Use fdisk to mount disks

View disk information

Use 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 preinstalled, run the following command to install it. If LVM is already installed, skip this step.
- 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
```
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
```
You can run the vgs command to view the volume group information.
Create a logical volume (LV)

Create a 100G logical volume from the VG. This is only an example; you can set the logical volume size based on your needs.
```
[root@test001 ~]# lvcreate -L 100G -n lv01 vg01
```
You can run the lvs command to view the logical volume information.

Format and mount

Format as ext4 file system:

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

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

Mount temporarily:

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

Enable automatic mounting at boot

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

View disk information

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

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

Format and mount

Format as ext4 file system:
```
[root@test001 ~]# mkfs.ext4 /dev/sdb1
```
Create a mount point:
```
[root@test001 ~]# mkdir -p /data/1
```

Mount temporarily:

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

Enable automatic mounting at boot

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

View disks

After mounting the disks, run the following command to check the disk layout:

[root@test001 ~]# df -h

The 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

Result description:

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

Ensure that the disks for data_dir, redo_dir (or clog_dir), and home_path in the configuration file have been mounted. The directories for data_dir and redo_dir must be empty. The disk usage for the data_dir directory must be less than 4%.

Set directory permissions

After mounting the disks, you need to check the permissions of the directories corresponding to the disk mount points. Run the following command to check the directory permissions of cluster-related files.

Taking the data directory as an example:

[root@test001 data]# ls -al

The following result indicates that the directory owner is the admin user in the admin group:

drwxr-xr-x 2 admin admin 4096 02/09 18:43 .
drwxr-xr-x 2 admin admin 4096 02/09 18:43 log1

If the admin user does not have the necessary privilege for the related files, run the following commands to change the file ownership:

[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.

(Optional) Perform disk planning

Note

Disk mounting

Mounting requirements

Note

Mount operations

Notice

View disks

Set directory permissions