This topic describes the limits of Apsara File Storage NAS on service specifications, operating systems, protocols, and the classic network.

Limits on service specifications

Maximum number of file systems that you can create within an Alibaba Cloud account in a single region 20
Maximum number of mount targets for each file system
  • General-purpose NAS file system: 2
  • Extreme NAS file system: 1
Maximum number of files in each file system 1 billion
Maximum directory levels of each file system 1,000 levels
Maximum capacity of each file system
  • Capacity NAS file system: 10 PiB
  • Performance NAS file system: 1 PiB
  • Extreme NAS file system: 256 TiB
Maximum number of compute nodes on which you can mount a file system at the same time 1,000
Maximum size of each file 32 TiB
Maximum number of hard links to each file 511

Limits on operating systems

  • Apsara File Storage NAS has tested the kernel images and listed the recommended images. To ensure the optimal performance of NAS file systems, use the recommended kernel versions or later versions. If you do not use the recommended kernel images, Apsara File Storage NAS may become unavailable. For more information, see Recommended kernel images.
  • Apsara File Storage NAS has identified some defective kernel versions and provided solutions. If you use a defective kernel version and do not upgrade the version, Apsara File Storage NAS may become unavailable. If Apsara File Storage NAS identifies new issues about the adaption of kernel versions, Apsara File Storage NAS will push notifications to you by using emails, internal messages, SMS messages, console announcements, and other methods. Make sure that the preceding communication channels are available and handle the issues at the earliest opportunity. For more information, see Known issues on an NFS client.
  • You can mount only Server Message Block (SMB) file systems on macOS.
  • Apsara File Storage NAS does not support Advanced Interactive eXecutive (AIX).

Limits on protocols

  • Network File System (NFS) file systems
    • The maximum length of a file name is 255 bytes.
    • NFSv4.0 does not support the following attributes: FATTR4_MIMETYPE, FATTR4_QUOTA_AVAIL_HARD, FATTR4_QUOTA_AVAIL_SOFT, FATTR4_QUOTA_USED, FATTR4_TIME_BACKUP, and FATTR4_TIME_CREATE. If you use an unsupported attribute, an NFS4ERR_ATTRNOTSUPP error is logged in the /var/log/messages file.
    • NFSv4.0 does not support the following operations: OP_DELEGPURGE, OP_DELEGRETURN, and NFS4_OP_OPENATTR. If you call an unsupported operation, an NFS4ERR_ATTRNOTSUPP error is logged in the /var/log/messages file.
    • NFSv4.0 does not support delegations.
    • NFSv4.1 is not supported.
    • The POSIX SetUID, SetGID, and Sticky Bits features are not supported.
    • UID and GID
      • In Linux, the mappings between user IDs (UIDs) and usernames and the mappings between group IDs (GIDs) and group names are defined in configuration files. For NFSv3 file systems, if the mapping between an ID and a name is defined in a configuration file, the name is used to represent the user or group. If no mapping is defined for an ID, the ID is used.
      • For NFSv4.0 file systems, the usernames and group names of all files are identified as nobody if the version of the Linux kernel is earlier than 3.0. If the kernel version is later than 3.0, the rule that is used by NFSv3 file systems applies.
        Note If the Linux kernel version is earlier than 3.0, we recommend that you do not run the chown or chgrp command for files or directories in an NFSv4.0 file system. Otherwise, the UID and GID of the file or directory are changed to nobody.
    • Limits on NFS clients
      • For General-purpose NAS file systems, an NFS client can send a maximum of 128 concurrent requests.
      • For General-purpose NAS file systems, the maximum bandwidth of an NFS client is 500 MB/s.
      • You can open a maximum of 32,768 files at a time on an NFS client. The files in the list folder and its subfolders are not counted.
      • Each mount on an NFS client can acquire up to 8,192 locks across a maximum of 256 file-process pairs. For example, a single process can acquire one or more locks on 256 separate files, or 8 processes can each acquire one or more locks on 32 files.
      • We recommend that you do not use an NFS client on an Elastic Compute Service (ECS) instance to access an NFS file system.
    • Extreme NAS file systems

      Extreme NAS file systems support the following types of files and directories: REG, DIR, SYMLINK, and LINK.

  • SMB file systems
    • The maximum length of a file name is 255 UTF-16 characters.
    • Limits on features
      • SMB file systems do not support extended file attributes and client-side caching based on leases.
      • SMB file systems do not support I/O control (IOCTL) or file system control (FSCTL) operations. For example, you cannot create sparse files, compress files, inspect the status of network interface cards (NICs), or create reparse points.
      • SMB file systems do not support alternate data streams.
      • SMB file systems do not support identity authentication that is provided by the Lightweight Directory Access Protocol (LDAP).
      • SMB file systems do not support the following features: SMB Direct, SMB Multichannel, SMB Directory Leasing, and persistent file handles.
    • Protocol versions

      We recommend that you use SMB 2.1 or later.

    • Limits on SMB clients

      Each file or directory can be opened a maximum of 8,192 times at a time. This limit applies across all compute nodes on which the file system is mounted and all users that share access to the file system. This indicates a maximum of 8,192 active file handles for each file or directory. A file system can have a maximum of 65,536 active file handles.

Limits on the classic network

  • You cannot mount a NAS file system on an ECS instance of another Alibaba Cloud account.
  • If the IP address of a mount target is changed due to kernel limits, the NAS file system may become inaccessible.

    In this case, Apsara File Storage NAS pushes notifications to you by using emails, internal messages, SMS messages, intelligent voice reminders, and console announcements 30 days in advance. Remount the file system within 30 days after the push date.