This topic describes the limits of resources, clients, and features in Apsara File Storage NAS.

Limits of resources

The following table lists limits of NAS resources.
Resource Description
Maximum number of file systems for each account in a region 20
Maximum number of mount targets for each file system

2

Limits of NFS clients

The following limits apply to Network File System (NFS) clients:

  • You can open a maximum of 32,768 files at a time on an NFS client. 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 files or processes. 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 in a Windows host to access an NFS file system.

Limits of 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 that have the file system 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 maximum of 65,536 active file handles can exist on a file system.

Limits of file systems

The following limits apply to NAS file systems:

  • Maximum number of files in each file system: 1 billion.
  • Maximum length of a file system name: 255 bytes.
  • Maximum directory depth: 1,000 levels.
  • Maximum capacity of each file system: 10 PB for NAS Capacity and 1 PB for NAS Performance.
  • Maximum number of compute nodes on which a file system is mounted: 1,000.
  • Maximum size of each file: 32 TB.
  • Each file supports up to 511 hard links.
  • In Linux, mappings between user IDs (UIDs) and usernames and 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 displayed. If no mapping is defined for an ID, the ID is displayed.
  • For NFSv4 file systems, the usernames and group names of all files are displayed 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.
  • 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 that are stored on a mounted NFSv4 file system. Otherwise, the UID and GID of the file or directory will be displayed as nobody.
  • NAS supports the SMB 2.1 protocol and later versions. NAS also supports operating systems including Windows 7, Windows Server 2008 R2, and later versions. However, NAS does not support Windows Vista, Windows Server 2008, or earlier versions. Compared with SMB 2.1 and later versions, SMB 1.0 provides lower performance and fewer features. Furthermore, Windows products that support only SMB 1.0 have reached end of support.

Unsupported NFS features

This section lists the NFS features that NAS does not support.

  • 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 one of the preceding attributes is used, an NFS4ERR_ATTRNOTSUPP error is recorded in the /var/log/messages file.
  • NFSv4.1 does not support the following attributes: FATTR4_DIR_NOTIF_DELAY, FATTR4_DIRENT_NOTIF_DELAY, FATTR4_DACL, FATTR4_SACL, FATTR4_CHANGE_POLICY, FATTR4_FS_STATUS, FATTR4_LAYOUT_HINT, FATTR4_LAYOUT_TYPES, FATTR4_LAYOUT_ALIGNMENT, FATTR4_FS_LOCATIONS_INFO, FATTR4_MDSTHRESHOLD, FATTR4_RETENTION_GET, FATTR4_RETENTION_SET, FATTR4_RETENTEVT_GET, FATTR4_RETENTEVT_SET, FATTR4_RETENTION_HOLD, FATTR4_MODE_SET_MASKED, and FATTR4_FS_CHARSET_CAP. If one of the preceding attributes is used, an NFS4ERR_ATTRNOTSUPP error is recorded in the /var/log/messages file.
  • NFSv4 does not support the following operations: OP_DELEGPURGE, OP_DELEGRETURN, and NFS4_OP_OPENATTR. If one of the preceding operations is performed, an NFS4ERR_ATTRNOTSUPP error is recorded in the /var/log/messages file.
  • NFSv4 does not support delegations.

Unsupported SMB features

NAS does not support the following SMB features:

  • Extended file attributes, and client-side caching based on leases.
  • Input/output control (IOCTL) or file system control (FSCTL) operations, such as creating sparse files, compressing files, inspecting the network interface card (NIC) status, and creating reparse points.
  • Alternate data streams.
  • Identity authentication that is provided by Active Directory (AD) or Lightweight Directory Access Protocol (LDAP).
  • Several features that are provided by SMB 3.0 or later, such as SMB Direct, SMB Multichannel, SMB Directory Leasing, and Persistent File Handle.
  • Access control lists (ACLs) on files or directories.