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    PolarDB:Common mount parameters of LakeBase

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    PolarDB:Common mount parameters of LakeBase

    Last Updated:Jul 13, 2026

    This topic describes the common PolarDB Agent LakeBase client mount parameters, including META-URL connection parameters, metadata cache parameters, and I/O configuration parameters.

    Mount command

    Mount a file system by running the lakebase-client mount command:

    lakebase-client mount [options] <META-URL> <MOUNTPOINT> --subdir=<SUB_DIR>

    Parameter

    Description

    META-URL

    The metadata engine URL. You can use the complete META-URL value obtained from the OpenAPI-DescribePolarFsAttribute, or obtain the MetaURL from the Basic Information page of the PolarDB Agent LakeBase instance.

    MOUNTPOINT

    The local mount point path.

    <SUB_DIR>

    Optional. The relative or absolute path of a subdirectory under the LakeBase root directory. For example, a/b/c or /a/b/c. This mounts the specified subdirectory to <MOUNT_POINT>. If not specified, the LakeBase root directory is mounted.

    Note

    When you Mount with a SidecarSet without specifying a subdirectory, you must remove the subPath: <SUB_DIR> line from the YAML file to mount the LakeBase root directory. In this case, all directories and files under the LakeBase root directory are visible to the pod.

    META-URL parameters

    META-URL supports appending connection parameters through the URL query string. You can specify the query string separately by using the --meta-url-query-string option. The client automatically appends the query string after decryption.

    # Specify parameters by using --meta-url-query-string
lakebase-client mount <META-URL> /mnt/lakebase -d --meta-url-query-string "max_open_conns=8&max_idle_conns=8"

    Metadata database parameters

    Parameter

    Default value

    Description

    max_open_conns

    8

    The maximum number of open database connections. Increase this value for high-concurrency workloads.

    max_idle_conns

    8

    The maximum number of idle connections in the connection pool. Set this value equal to max_open_conns for optimal performance.

    Metadata configuration parameters

    These parameters define the local metadata caching strategy for the client. Proper caching configuration reduces the number of round-trips to the metadata engine and improves the response speed of high-frequency operations such as ls (list directory), stat (query attributes), and open (open file).

    Parameter

    Type

    Default value

    Description

    --skip-dir-mtime

    string

    "100s"

    When a file is created or deleted in a directory, the mtime update is skipped if the interval since the last update is within this duration. This reduces metadata write amplification for high-frequency directory operations.

    --attr-cache

    string

    "1s"

    The kernel cache TTL for file attributes such as size, permissions, and mtime. After expiration, the next stat call queries the metadata engine again.

    --entry-cache

    string

    "1s"

    The kernel cache TTL for filename-to-inode mappings. After expiration, the next lookup operation queries the metadata engine again.

    --dir-entry-cache

    string

    "1s"

    The kernel cache TTL for directory entry lists. After expiration, the next readdir call queries the metadata engine again.

    --open-cache

    string

    "0s"

    For previously opened files, subsequent open or getattr calls within this time window return cached attributes without querying the metadata engine. Set to 0 to disable this cache.

    --open-cache-limit

    uint64

    10000

    The maximum number of files tracked by the open cache. When this soft limit is exceeded, the earliest opened files are evicted from the cache.

    I/O configuration parameters

    These parameters tune the memory buffer, prefetch strategy, and network concurrency of the client, which directly determine the I/O throughput and latency performance.

    Parameter

    Type

    Default value

    Description

    --max-fuse-io

    string

    "1024K"

    The maximum data size per read/write request that the kernel sends to the client. Larger values reduce the number of context switches between kernel space and user space. The actual upper limit depends on the kernel version.

    --buffer-size

    string

    "300M"

    The total memory buffer pool shared by all concurrent read and write operations. Approximately 80% of this buffer is allocated to the prefetch buffer. The minimum value is 32 MiB.

    --max-uploads

    int

    50

    The number of goroutines that concurrently upload data blocks to object storage in the background. Higher values improve write persistence speed but increase request pressure on the object storage service.