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The Dell Unity File System addresses the growing demand for larger file systems and protocol flexibility. Dell Unity File System is a 64-bit file system architecture that offers large-scale limits on the number of files per directory, the number of subdirectories per directory, and a maximum capacity of 256 TB. Table 2 provides more information about the scale of Dell Unity File System.
For a full list of available Dell Unity File System limits and other system limits, see the Dell Unity Simple Support Matrix on the Dell website.
Item | Limit |
MAX FILE SYSTEM SIZE | 256 TB |
SUBDIRECTORIES PER DIRECTORY | ~100 Million |
FILES PER FILE SYSTEM | ~32 Billion |
FILE NAMES PER DIRECTORY | ~10 Million |
ACL IDS | 4 Million |
To provision a Dell Unity File System, a NAS Server is required. Dell Unity File Systems can be accessed through SMB or NFS protocols and can be shared to both protocols simultaneously by using a Multiprotocol file system.
NAS Servers host file systems on the Dell Unity storage system. NAS Servers use virtual interfaces to enable host connectivity to SMB, NFS, and Multiprotocol file systems, as well as VMware NFS Datastores and VMware Virtual Volumes. Depending on what is enabled on the NAS Server, SMB file systems and NFS file systems can be created either separately or in a multiprotocol configuration. File systems and virtual interfaces are isolated to a single NAS Server, allowing for multitenancy over multiple NAS Servers. NAS Servers are hosted on a Storage Processor and will automatically fail over in the event the SP becomes faulted. Any associated file systems will also be failed over.
Dell Unity OE version 5.4 introduced the ability to grant or restrict SMB share access to specific hosts from the Unity system. Prior to Dell Unity OE version 5.4, only NFS Exports allowed users to grant or restrict access to specific hosts. Dell Unity OE 5.4 brings parity to the SMB protocol where a user can grant or restrict access to a Share for the SMB protocol. Dell Unity OE 5.4 also introduced the ability to disable not only SMB version 1.0 but also the SMB 2.0 dialects for better security.
Dell Unity OE version 4.5 introduced the ability to create shares for writable and read-only snapshots on the destination NAS Server. This feature is designed to enable DR testing without any impact to the ongoing replication. It allows customers to confirm that an application can be successfully brought online and write to a share hosted on the destination system. This feature works with both asynchronous and synchronous replication. This feature leverages a Proxy NAS Server and Proxy share created on the destination system to provide access to the snapshot.
Starting with Dell Unity OE version 4.4, ports can be configured for a custom MTU size 1280 through 9216. Previously, the MTU sizes were limited to either 1500 or 9000. The custom MTU size can be configured on ports that are used for NAS Server, replication, and import interfaces. Any ports that have iSCSI interfaces created must still use 1500 or 9000.
Dell Unity OE version 4.4 also included several NFS enhancements; for example, NFS share names can contain the “/” character. Previously, using the “/” character in the share name was prohibited because it was reserved to indicate a directory on UNIX systems. Allowing the use of the “/” character in the share name enables administrators to create a virtual namespace that is different from the path used by the share. Dell Unity OE version 4.4 also introduced the ability to allow or prevent clients from setting the setuid and setgid bits on any files and directories residing on the NFS share. By default, this is allowed and can be changed when creating or modifying an NFS share. Dell Unity OE version 4.4 also introduced the ability to configure the anonymous UID and GID attributes.
In Dell Unity OE version 4.3, LDAP enhancements were added, such as the ability to run LDAP lookups from the NAS Server. This is useful for confirming the mappings are configured properly and also for troubleshooting purposes. Dell Unity OE version 4.3 also introduced dynamic LDAP. Dynamic LDAP provides the ability to automatically obtain the LDAP server IP addresses and ports when configuring or editing a NAS Server. Additional enhancements in this release include improvements to unmapped users, automatic mapping for unmapped windows accounts, secmap cache management, and read-only proxy NAS Servers. Read-only proxy NAS Servers provide the ability to access all the file system and snapshot data on the destination NAS Server through SMB and NFS.
In Dell Unity OE version 4.2.1, enhancements to Link Aggregation and the introduction of Fail-Safe Networking (FSN) improved NAS Server high availability. Link Aggregation combines multiple network connections into a logical link, increasing throughput by distributing traffic across multiple connections and providing redundancy in case one connection fails. If a connection loss is detected, the link is immediately disabled and traffic is automatically moved to the surviving links in the aggregate. Dell Unity OE version 4.2.1 improved Link Aggregation, allowing ports from different I/O Modules or onboard Ethernet ports to be aggregated together. Fail-Safe Networking is a high availability feature that extends link failover into the network by providing switch-level redundancy. FSN is created from Ethernet ports, link aggregations, or any combination of the two, and appears as a single link with a single MAC address and potentially multiple IP addresses. FSN does not require any configuration from the switch side, this allows a single FSN to be connected to multiple switches, providing availability if a switch fails.
Dell Unity OE version 4.2 added the ability to modify NAS Server parameters at a NAS Server level. In prior releases, only global NAS Server parameters could be modified. Modifying parameters at a per-NAS Server level gives greater flexibility in environments where not all NAS Servers need the same configuration. These parameters can be modified by using the svc_nas command.
Dell Unity OE version 4.1 introduced IP Multi-Tenancy, which adds the ability to provide network isolation for tenants. This feature separates network traffic at the kernel level on the SP, enabling the ability to provide dedicated network resources for each tenant. Each tenant has its own dedicated network namespace including VLAN domain, routing table, firewall, interfaces, DNS, and more. This also enables the ability for multiple tenants to use the same IP network configuration, so IPs can be duplicated across tenants. This avoids network interference between tenants and also enhances security. This feature is only available on purpose-built Dell Unity systems; it is not available on Dell UnityVSA.
On a NAS server, interfaces can be configured to enable communication between the NAS Server, client, and external services. In addition, starting with Dell Unity OE version 4.1, static routes can also be configured to determine where to forward a packet so that it can reach its destination. Static routes can either be a host or network route. A host route is the most specific type of route, which is only used when traffic is sent to a specific IP address. A network route is less specific and is used when sending traffic to a specific subnet. The system uses the most specific route available. If no host or network routes are defined, the default route is used (if configured).
Packet Reflect, available in Dell Unity OE version 4.1 or later, is a feature that ensures outbound (reply) packets are sent back to the same host or router as the inbound (request) packet. This enables the NAS Server to bypass routing and ARP table lookups when replying to a packet, so no routing configuration is required.
In Dell Unity OE version 4.1, for multiprotocol NAS Servers, users can use local files to resolve UNIX user identities for their UNIX Directory Service (UDS) configuration. This is useful in cases where an external NIS or LDAP server is not available for UDS configuration, but multiprotocol is still needed to provide an easy alternative without requiring an external service. Local files can be used to resolve UNIX user records in multiple ways, including by password, group, hosts, netgroup, and home directories. Dell Unity provides the ability to perform operations such as failover, failback, pause, and resume on individual NAS Servers and file systems with replication enabled. For example, to initiate a failover, you must first failover the NAS Server and then failover the individual file systems to enable access on the destination system. Dell Unity OE version 4.2 and later provides an enhancement to this process, with automatic failover of all the associated file systems once a failover is initiated on the NAS Server.
For more information about NAS Servers, see the Dell Unity: NAS Capabilities white paper.
Dell Unity allows users to connect to a Common Anti-Virus Agent (CAVA) which can be used to identify and eliminate known viruses before they infect files on a system. CAVA is enabled by the Dell Common Event Enabler (CEE) framework which is available for download and install for Windows or Linux environments. CAVA is for the CIFS/SMB protocol and does not support the NFS protocol.
Starting in Dell Unity OE version 4.1, the system can connect to a Common Event Publishing Agent (CEPA) using the existing CEE framework. CEPA is a mechanism that allows applications to receive file event notifications (that is receive notifications when a file is created, opened, edited, renamed, and so on). CEPA is available for CIFS/SMB protocol and is configurable in a NAS Server’s properties.
For more information about CEE, CAVA, and CEPA, see the technical papers titled Using the Common Event Enabler for Windows and Using the Common Event Enabler for Linux on Dell Support. For a full list of supported anti-virus products, see the Dell Unity Simple Support Matrix on the Dell website.
File systems are file-based storage resources that are hosted on NAS Servers. They are accessed through Shares, which can be provisioned for SMB access or NFS access. This provides access for Windows and UNIX hosts. Depending on what protocol is selected for your file system, only shares of that type can be provisioned. For example, if an SMB file system is created, SMB Shares (not NFS) can be provisioned. To provision both SMB and NFS Shares from a file system, the SMB and NFS protocols in the NAS Server must be enabled or a multiprotocol file system must be used.
Starting with Dell Unity OE version 4.4, NFS host registration is made optional. Instead, host access can be managed by specifying a comma-separated string. This is designed to simplify management and improve ease of use. If replication is configured, this string is also replicated to the destination so no reconfiguration of host access is required if a failover occurs.
Dell Unity supports up to SMB 3.02 including older CIFS versions and NFS v3, 4.0, and 4.1. In Dell Unity OE version 4.2 and later, the system supports SMB 3.1.1, which adds reliability enhancements for Continuous Availability for Hyper-V Cluster Client Failover and improved security and encryption traffic performance. Secure NFS using Kerberos is also supported. FTP and SFTP can be enabled on a NAS Server, providing access to provisioned file systems over these protocols. File systems can be extended and shrunk in size, and allocated space is automatically taken and reclaimed based on file system usage patterns. Finally, file systems can be configured with quotas to better regulate file system space usage. Tree quotas and user quotas are supported on file systems, and can be used in combination.
Multiprotocol file systems are created on multiprotocol NAS Servers. A multiprotocol NAS Server must use Active Directory services and either NIS or LDAP. A multiprotocol file system relies on the directory services running in each of the Windows and UNIX environments, by matching the username in one environment to the identical username in the other. For discrepancies between usernames in each environment, an ntxmap may be uploaded to the multiprotocol NAS Server. Additionally, a default user may be assigned for each environment so that a username who does not have an equivalent account in the other environment can still access the file system.
For more information about Dell Unity file systems, see the Dell Unity: NAS Capabilities white paper.
Dell Unity OE version 4.5 introduces File-Level Retention (FLR). FLR enables the ability to lock files, preventing them from being modified or deleted until a specified retention date. This functionality is also known as Write Once, Read Many (WORM). FLR is available on the physical Dell Unity Family and on Dell UnityVSA systems. This feature is only available for file systems and is not available for VMware NFS datastores.
There are two versions of FLR available – Enterprise (FLR-E) and Compliance (FLR-C). FLR-E prevents file modification and deletion by users through access protocols such as SMB, NFS, and FTP. However, an authorized storage administrator can delete the entire file system even if it contains locked files. FLR-C prevents administrators from deleting a file system that contains locked files. The administrator must wait for all files to expire before the file system can be deleted. FLR-C also has other differences including a data integrity check, hard infinite retention, and snapshot restrictions. FLR-C is designed to meet the requirements of SEC Rule 17a-4(f).
For more information about File Level Retention, see the Dell Unity: File-Level Retention white paper.
ESXi and Linux hosts can be given access to VMware NFS Datastores. VMware NFS Datastores, similar to VMware VMFS Datastores, are storage resources that will be automatically formatted and added to a VMware vCenter environment, allowing for efficient deployment of resources in a VMware environment. As the name implies, VMware NFS Datastores are accessed over the NFS protocol. Accordingly, a NAS Server with NFS protocol support must be available to configure VMware NFS Datastores. Also, starting with Dell Unity OE version 4.2, VMware NFS datastores can be mounted using NFSv4 protocol. When creating NFS datastores on earlier versions of Dell Unity OE, the NFSv3 protocol is always used.
VMware Virtual Volumes are also available to be served over a file protocol. NFS mount points may be defined by a Protocol Endpoint for a VMware environment to receive vVol Datastore access. A NAS Server with NFS protocol support must be available to configure VMware Virtual Volumes over file.
For more information about VMware datastores, Virtual Volumes, and other virtualization technologies related to Dell Unity, see the Dell Unity: Virtualization Integration white paper.