Network-attached storage (NAS) features and product guide

Clustered or scale-out NAS

Nowadays, NAS products often offer increased scalability and performance compared to the standalone boxes of yesteryear. NAS' ability to scale its capacity means it's increasingly being used in clusters that mirror the growth in compute clusters.

So-called clustered or scale-out NAS dispenses with the idea of storage controllers or NAS filer heads. The architecture comprises hardware nodes that contain disk, cache and CPU resources with a node being a peer in a cluster.

Among the benefits of scale-out NAS are single name space, which allows users and applications to access and search data scattered across geographical locations and clustered storage devices without needing to know their location; data protection features, such as data backup and replication; flexibility, to grow or shrink capacity by adding or removing devices; ease of management; and the ability to use a single storage management system across multiple devices.

Scale-out/clustered NAS is well-suited to high-volume, small file size content serving, such as delivering online services to consumers.

Data deduplication

Data deduplication technology is often incorporated into NAS devices. Data deduplication means the storage system retains only one of multiple copies of a piece of data, removing later iterations while inserting a pointer to the original.

It is commonly used for compressing backups before the data is sent to the virtual tape library (VTL). For example, backing up a department full of Windows PCs would otherwise mean moving and storing dozens of gigabytes of identical OS and program data per machine.

Flash drives

Seen primarily in the form of USB-attached memory, flash memory can be found in some enterprise NAS products. Its lack of moving parts mean it consumes less space and energy and, in the right configuration, it is faster. Vendors such as Sun Microsystems and EMC have added flash-based storage into some of their products to insert a tier zero above the existing tiers in a tiered architecture for highly transactional access that can take the best advantage of its speed.

Multiprotocol access

Traditionally, direct-attached storage (DAS) was accessed using SCSI protocols. When storage moved away from the processing unit, FC allowed the reach of SCSI's block-level access to storage media to be extended over much longer distances. Fibre Channel is most commonly used for attaching SANs, while NAS devices use either CIFS- or NFS-based file-level access over Ethernet links. Today, many network-attached storage devices – offering so-called multiprotocol or unified storage -- can also attach using FC and, more recently, iSCSI, which allows block-level access over IP via an Ethernet link, which means access to storage can be global.

NAS gateways

NAS devices are also deployed as front-end devices, gateways or heads for storage-area networks (SANs), where they act as file servers. In this role they manage block-level storage over Fibre Channel (FC) or iSCSI links.

Replication

Replication is the process of ensuring that a second copy of the data always exists. Array-based replication means there is a duplicate NAS that contains a mirror of the data. While most RAID configurations provide array-based replication, some also offer network replication, which means intercepting data being sent to and from the hosts, and copying it to another, usually remote, location.

Thin provisioning

Thin provisioning is a common feature in the latest NAS products. It allows storage managers to provision more storage to applications than is physically present, meaning you only buy capacity when it is actually needed, which improves utilisation. Compared to the traditional model of buying all provisioned storage upfront, this cuts capital and operational expenditures and you don't pay for the energy needed to spin and cool empty disks.

Tiered storage

Tiering involves moving infrequently accessed data onto cheaper storage. For example, high-speed but costly NAS devices might contain production data for live projects but, if a file hasn't been accessed for a given time -- maybe 90 days -- then it can be moved to a cheaper set of lower-performing disks. In a three-tier system, a file would be archived off to tape after a further period, maybe a year. An automated, policy-based system can perform these tasks, creating file pointers on higher tiers so that users can still access the files.

Virtual tape libraries

Virtual tape library functionality is included in some NAS products. VTLs are designed to look like tape drives and libraries from the point of view of the backup software, but consist of disks. They are often used in front of real tape libraries to speed access to infrequently accessed data and, because disks are faster than tape, to shorten backup windows.

Vendor/product guide

Vendors that sell their own NAS technologies are relatively few: many resell or adapt the technology of others. Fujitsu sells a number of vendors' devices, Hitachi Data Systems resells BlueArc, IBM resells NetApp, and HP and Dell use Microsoft Windows Storage Server and Linux as the basis for their NAS products. Management software adds such features as data deduplication, replication and thin provisioning.

Feature overlap across vendor offerings is very high, so most vendors offer features such as deduplication, tiering and thin provisioning, along with multiprotocol access, including iSCSI. The main differentiation inside vendor products remains capacity, performance and I/O capability, as well as added features such as data policy-based tools for data migration across tiered infrastructures and storage virtualisation.

BlueArc
Mercury series
Max capacity (native): 2 PB
Max ports: six 1 GbE, two 10 GbE, four Fibre Channel
Key features: Single name space across clusters up to eight nodes; supports iSCSI, NFS and CIFS, policy-based migration, tiering, thin provisioning

Titan series (two products)
Max capacity (native): 4 PB
Max ports: two 10 GbE or six 1 GbE, eight Fibre Channel
Key features: Single name space across clusters up to eight nodes; supports NFS and CIFS, policy-based migration and tiering across multiple storage technologies, thin provisioning

EMC
Celerra NAS
NX4
Max capacity (native): 60 TB
Ports: Four 1 Gbps, or two 10 Gbps and two 1Gbps, plus four Fibre Channel per blade with maximum of two blades
Key features: Supports CIFS, NFS, FTP Secure and FTP, hot swap power/cooling

NS-120
Max capacity (native): 64 TB
Max ports: Eight 1 Gbps, or four 1Gbps and four 10 Gbps, plus four Fibre Channel per blade with maximum of two blades
Key features: Multiprotocol SAN filer, data deduplication, virtual provisioning, automated volume management

NS-480
Max capacity (native): 192 TB
Max ports: Eight 1 Gbps (copper or optical) or four copper 1 Gbps and four optical 10 Gbps, plus four Fibre Channel per blade with maximum of four blades
Key features: Supports multiple SANs, data deduplication, file-level retention; multiprotocol SAN gateway; addresses FC, SATA and flash drives

NS-960
Max capacity (native): 740 TB
Max ports: Two 10 Gbps, four copper 1Gbps, four optical 1Gbps per blade, plus four 4 Gbps or 8 Gbps Fibre Channel with maximum of eight blades
Key features: 960-drive capacity; n+1 or n+m failover; multiprotocol SAN gateway; data deduplication; file-level retention; addresses FC, SATA and flash drives

Celerra Gateway
NS-G2
Max capacity: 128 TB
Max ports: Four Fibre Channel, four 1 Gbps or two 10 Gbps and two 1Gbps per blade with maximum of two blades
Key features: Multiprotocol SAN gateway, file-level retention, data deduplication

NS-G8
Max capacity (native): 896 TB
Max ports: Four Fibre Channel, two 10 Gbps and eight 1 Gbps, per blade with maximum of eight blades
Key features: Multiprotocol SAN gateway, file-level retention, data deduplication, n+1 or n+m failover for availability

Hewlett-Packard
X1000 range (12 products)
Max capacity: 96 TB (X1800)
Max ports: Four 1 Gbps
Key features: Entry-level Windows Storage Server-powered unified storage with eight drive slots

X3000 range (five products)
Max capacity (native): 292 GB
Max ports: Four 1 Gbps
Key features: Entry-level Windows Storage Server-powered gateway/filer connecting to SAN and high-availability cluster up to 16 nodes over CIFS, NFS and HTTP

X5000 range (four products)
Max capacity (native): 192 GB
Max ports: Four 1 Gbps, two 8 Gbps Fibre Channel
Key features: SUSE Linux-based gateway/filer connecting to SAN/iSCSI; 128 TB per CIFS, NFS or HTTP file system; 512 file systems/cluster with Linux; 256 file systems/clusters with Windows

X9000 range (six products)
Max capacity (native): 656 TB
Max ports: Eight 1 Gbps, two 10 Gbps, two Infiniband
Key features: Single namespace scales out to 16 PB, redundant drives/PSU/fans/controllers, storage rebalancing, policy management and file migration, remote replication, virtualisation

Hitachi Data Systems
3000 Series (four products)
Max capacity (native): 4 PB
Max ports: Four 10 GbE, eight 1 GbE or two 10 Gbps, eight Fibre Channel
Key features: File tiering with 'WORM' capability; single name space across clusters up to eight nodes; thin provisioning; supports iSCSI, NFS CIFS

IBM
System Storage N3000 Series (two products)
Max capacity (native): 104 TB
Max ports: 12 Fibre Channel, eight 1 Gbps
Key features: Entry-level NAS; supports iSCSI, CIFS, snapshotting, data deduplication, RAID 6; custom OS; single mailbox recovery

System Storage N6000 Series (six products)
Max capacity (native): 840 TB
Max ports: Eight Fibre Channel, four 1 GbE
Key features: Supports Fibre Channel over Ethernet (FCoE), iSCSI, NFS and CIFS, block and file level access, snapshotting, data deduplication, RAID 6, 10 Gbps;, custom OS, 64-bit architecture

System Storage N7000 Series (two products)
Max capacity (native): 1,176 TB
Max ports: 52 1 Gbps, 56 Fibre Channel
Key features: Manage non-native SANs; supports FCoE, iSCSI, NFS, and CIFS, block and file level access, clustering, snapshotting, data deduplication, RAID 6, 10 Gbps; custom OS

NetApp
NAS
FAS2000 series (three products)
Max capacity (native): 136 TB
Ports: eight 8 Gbps Fibre Channel, eight 1 Gbps
Key features: Entry-level NAS; supports iSCSI, CIFS, snapshotting, data deduplication, RAID 6; custom OS

FAS3100 series (three products)
Max capacity (native): 840 TB
Max ports: 40 Fibre Channel, 36 1 GbE
Key features: Supports FCoE, iSCSI, NFS and CIFS, block- and file-level access, snapshotting, data deduplication, RAID 6, 10 Gbps; custom OS; 64-bit architecture

FAS6000 series (two products)
Max capacity (native): 1,176 TB
Max ports: 52 1 Gbps, 56 Fibre Channel
Key features: Manage non-native SANs; supports FCoE, iSCSI, NFS and CIFS, block- and file-level access, snapshotting, data deduplication, RAID 6, 10 Gbps; custom OS

Gateways
V6000 series (two products)
Max capacity (native): 1,176 TB
Max ports: 52 1 Gbps, 56 Fibre Channel
Key features: Multivendor SAN/NAS gateway; storage virtualisation; custom OS; supports FCoE, iSCSI, NFS and CIFS, snapshotting, data deduplication

V3100 series (three products)
Max capacity (native): 840 TB
Max ports: 40 Fibre Channel, 36 1 GbE
Key features: Multivendor SAN/NAS gateway; storage virtualization; custom OS; supports FCoE, iSCSI, NFS and CIFS, snapshotting, data deduplication

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