Cloud Parallel File Storage:Limitations

Mounting limitations

• Supported clients: Lingjun resources, Platform for AI (PAI) general-purpose computing resources, PAI Lingjun resources (single-tenant), and Container Compute Service (ACS) (for high-performance network GPU-accelerated workloads).

• Unsupported: Direct mounting from ECS instances.

• Protocol: Only the POSIX protocol is supported.

File system limitations

Directory naming constraints

To ensure system stability and support for enterprise features, CPFS for Lingjun reserves specific directory names. If you attempt to create a directory with a reserved name, the system returns an EPERM error. There are two categories of reserved names:

• Reserved only in the file system root directory: An EPERM error is returned only if you attempt to create a directory with one of these names in the file system root directory.

• Reserved in all directories: An EPERM error is returned if you create a directory with one of these names at any level within the file system.

Operating system limitations

The CPFS for Lingjun client supports only Linux operating systems, such as Alibaba Cloud Linux and Ubuntu. The following table lists the supported versions.

Scale-out limitations

• CPFS for Lingjun file systems only support scale-out, not scale-in.

• Scale-out increment: 10,240 GiB. You can scale out a file system to a maximum of 1 PiB.

  To create a file system with up to 20 PiB of capacity, submit a ticket.

For capacity specifications, see Product specifications.

Dataflow limitations

• Dataflow

  • Same-account dataflows require CPFS for Lingjun 2.4.0 or later. Cross-account dataflows require 2.6.0 or later.

  • Maximum 10 dataflows per CPFS for Lingjun file system.

  • Each file system path can link to only one OSS bucket.

  • Dataflows cannot span different regions.

• Restrictions on paths, filenames, and directory names

  • Renaming a non-empty directory in a dataflow-associated path returns a Permission Denied or directory-not-empty error.

  • Use special characters in directory and file names with caution.

    • Supported characters include uppercase and lowercase letters, numbers, exclamation points (!), hyphens (-), underscores (_), periods (.), asterisks (*), and parentheses (()).

    • The following characters are not supported and may cause task failures:

      • A subdirectory or file name cannot be "..".

      • A path cannot contain backslashes (\) or consecutive backslashes (\\).

      • A subdirectory or file name cannot contain forward slashes (/).

  • Maximum path length: 1,023 characters.

• Dataflow task limitations

  • Streaming tasks require CPFS for Lingjun 2.6.0 or later and are API-only.

  • Maximum four concurrent batch tasks per dataflow. Concurrent streaming tasks are unlimited.

  • Import limitations

    • Importing a symbolic link converts it into a regular data file. The symbolic link information is lost.

    • If an OSS bucket has versioning enabled, only the latest version of an object is copied.

    • Filenames or subdirectory names cannot exceed 255 bytes.

  • Export limitations

    • Symbolic links are exported as regular, empty objects. The linked file is not synchronized.

    • Hard links are exported as regular files.

    • Socket, Device, and Pipe files are exported as regular, empty objects.

    • Directory paths cannot exceed 1,023 characters.

Fileset limitations

• Filesets

  Limitation	Description
  File system	Filesets are supported only on CPFS for Lingjun 2.7.0 and later.
  Number of filesets per file system	The default quota is 500. To request a higher quota, up to 3,000, submit a ticket.
  Number of files or directories per fileset	10 billion
  Fileset	If a parent directory is already a fileset, its subdirectories cannot be. Creating hard links or renaming across filesets is not supported.
  Fileset path	The path must start and end with a forward slash (/). The path must not already exist. The fileset path cannot be modified. If the fileset path contains multiple directory levels, the parent directory must already exist. The maximum path depth is 8 levels. The root directory (/) is level 0. For example, the path /workspace/dir1/ has a depth of 2. The maximum total path length is 990 characters. Each directory name can be up to 255 characters long and can contain uppercase and lowercase letters, digits, underscores (_), periods (.), and hyphens (-).
  Fileset deletion	You can delete a fileset only from the console or by using an API. After deletion, the system gradually releases the disk space. Deleted data is unrecoverable. Proceed with caution.

• Fileset quotas

  Limit	Description
  File system	Only CPFS Compute Edition 2.7.0 and later versions support Fileset quotas.
  Quota	Only one quota is supported for each Fileset path.
  Quota capacity	The minimum capacity is 10 GiB, with a scale-out increment of 1 GiB.
  Quota file count	The minimum file count is 10,000, with a scale-out increment of 1. The maximum limit is 10 billion.
  Quota write	If the data written to a Fileset reaches the capacity quota or the number of files written reaches the file count quota, no new data can be written.
  Quota statistics	Quota statistics have approximately a 15-minute latency. The current actual usage will take effect after approximately 15 minutes.
  Modify quota	When you modify a directory quota, the specified quota capacity or file count must be higher than the used capacity or file count. Otherwise, an error occurs.