NetApp filer

NetApp filer

In computer storage, NetApp filer, known also as NetApp Fabric-Attached Storage (FAS), or NetApp's network attached storage (NAS) device are NetApp's offering in the area of Storage Systems. A FAS functions in an enterprise-class Storage area network (SAN) as well as a networked storage appliance. It can serve storage over a network using file-based protocols such as NFS, CIFS, FTP, TFTP, and HTTP. Filers can also serve data over block-based protocols such as Fibre Channel (FC), Fibre Channel over Ethernet (FCoE) and iSCSI.[1] NetApp Filers implement their physical storage in large disk arrays.

Most other large storage vendors' filers tend to use commodity computers with an operating system such as Microsoft Windows Storage Server or tuned Linux. NetApp filers use highly customized hardware and the proprietary Data ONTAP operating system, both originally designed by founders David Hitz and James Lau specifically for storage-serving purposes. Data ONTAP is NetApp's internal operating system, specially optimised for storage functions at high and low level, it is booted from FreeBSD as a stand-alone kernel-space module and use some functions of FreeBSD (command interpreter and drivers stack, for example).

All filers have battery-backed NVRAM, which allows them to commit writes to stable storage quickly, without waiting on disks. Early filers connected to external disk enclosures via SCSI, while modern models (as of 2009) use FC and SAS protocol. The disk enclosures (shelves) support FC hard disk drives, as well as parallel ATA, serial ATA and Serial attached SCSI.

Implementers often organize two filers in a high-availability cluster with a private high-speed link, either Fibre Channel, InfiniBand, or 10G Ethernet. One can additionally group such clusters together under a single namespace when running in the "cluster mode" of the Data ONTAP 8 operating system.


Internal architecture

Most NetApp filers consist of customized computers with Intel or AMD processors using PCI. Each Filer has a proprietary NVRAM adapter to log all writes for performance and to play the data log forward in the event of an unplanned shutdown. One can link two filers together as a cluster, which NetApp (as of 2009) refers to using the less ambiguous term "Active/Active".

The Data ONTAP operating system implements a single proprietary file-system called WAFL. When used for file storage, Data ONTAP acts as an NFS server and/or a CIFS server, serving files to both Unix-like clients and to Microsoft Windows clients from the same file systems. This makes it possible for Unix and Windows to share files by the use of three security styles: mixed, ntfs, and unix. Data ONTAP supports user, group, and tree-based quotas (referred to as q-trees) and allows for data segregation and management within volumes. Qtrees with the UNIX security style will preserve the standard Unix permission-bits, the NTFS security style will preserve NT ACLs found in the Windows environment, and the mixed security allows the use of both interchangeably (with minor loss of fidelity). Since 2002, all NetApp FAS systems can also work as SAN storage over "block-based" protocols - FC, iSCSI, FCoE (since 2007).

Each filer model comes with a set configuration of processor, RAM and NVRAM, which users cannot expand after purchase. With the exception of some of the entry point storage controllers, the NetApp filers have at least one PCIe-based slot available for additional network, tape and/or disk connections. In June 2008 NetApp announced the Performance Acceleration Module (or PAM) to optimize the performance of workloads which carry out intensive random reads. This optional card goes into a PCIe slot and provides additional memory (or cache) between the disk and the filer RAM/NVRAM, thus improving performance.

NetApp supports either SATA, Fibre Channel, or SAS disk drives, which it groups into RAID (Redundant Array of Inexpensive Disks or Redundant Array of Independent Disks) groups of up to 28 (26 data disks plus 2 parity disks). Multiple RAID groups form an "aggregate"; and within aggregates Data ONTAP operating system sets up "flexible volumes" to actually store data that users can access. An alternative is "Traditional volumes" where one or more RAID groups form a single static volume. Flexible volumes offer the advantage that many of them can be created on a single aggregate and resized at any time. Smaller volumes can then share all of the spindles available to the underlying aggregate. Traditional volumes and aggregates can only be expanded, never contracted. However, Traditional volumes can (theoretically) handle slightly higher I/O throughput than flexible volumes (with the same number of spindles), as they do not have to go through an additional viritualisation layer to talk to the underlying disk.

WAFL, as a robust versioning filesystem, provides snapshots, which allow end-users to see earlier versions of files in the file system. Snapshots appear in a hidden directory: ~snapshot for Windows (CIFS) or .snapshot for Unix (NFS). Up to 255 snapshots can be made of any traditional or flexible volume. Snapshots are read-only, although Data ONTAP 7 provides additional ability to make writable "virtual clones", based at "WAFL snapshots" technique, as "FlexClones".

Data ONTAP implements snapshots by tracking changes to disk-blocks between snapshot operations. It can set up snapshots in seconds because it only needs to take a copy of the root inode in the filesystem. This differs from the snapshots provided by some other storage vendors in which every block of storage has to be copied, which can take many hours.

Snapshots form the basis for NetApp disk replication technology SnapMirror, which effectively replicates snapshots between two NetApp filers. Later versions of Data ONTAP introduced cascading replication, where one volume could replicate to another and then another etc. NetApp also offers a backup product based around replicating and storing snapshots, called SnapVault. Open Systems SnapVault allows Windows and UNIX hosts to back up data to a NetApp filer and store any filesystem changes in snapshots.

Data ONTAP also implements an option called "SyncMirror" where all the RAID groups within an aggregate or traditional volume can be duplicated to another set of hard disks, typically at another site via a Fibre Channel link. NetApp provides a "MetroCluster" option, that uses "SyncMirror" to provide a geo-cluster or active/active cluster between two sites up to 100 km apart.

Other product options include "SnapLock" which implements a "Write Once Read Many" functionality on magnetic disks instead of to optical media, so that data cannot be deleted until its retention period has been reached. SnapLock exists in two modes: compliance and enterprise. The compliance mode was designed to assist organizations in implementing a comprehensive archival solution that meets strict regulatory retention requirements such as dictated by the SEC and several healthcare governing bodies. Records and files committed to WORM storage on a SnapLock Compliance volume cannot be altered or deleted before the expiration of their retention period. Moreover, a SnapLock Compliance volume cannot be destroyed until all data have reached the end of their retention period.

SnapLock Enterprise is geared toward assisting organizations that are more self-regulated and want to have greater flexibility in protecting digital assets with WORM-type data storage. Data stored as WORM on a SnapLock Enterprise volume are protected from alteration or modification with one main difference from SnapLock Compliance: as the files being stored are not for strict regulatory compliance, a SnapLock Enterprise volume can be destroyed by an administrator with root privileges on the FAS system containing the SnapLock Enterprise volume, even if the designed retention period has not yet passed. In both modes, the retention period can be extended, but not shortened, as this is incongruous with the concept of immutability. In addition, NetApp SnapLock data volumes are equipped with a tamper-proof compliance clock that is used as a time reference to block forbidden operations on files, even if the system time is tampered with.

NetApp also offers products for taking application-consistent snapshots by coordinating the application and the NetApp Storage Array. These products support Microsoft Exchange, Microsoft SQL Server, Microsoft Sharepoint, Oracle, SAP and VMware ESX Server data. These products form part of the SnapManager suite.

Previous limitations

Prior to the release of ONTAP 8, individual aggregate sizes were limited to a maximum of 2TB for FAS250 models and 16TB for all other models.

The limitation on aggregate size, coupled with increasing density of disk drives, served to limit the performance of the overall system. NetApp, like most storage vendors, increases overall system performance by parallelizing disk writes to many different spindles (disk drives). Large capacity drives, therefore limit the number of spindles that can be added to a single aggregate, and therefore limit the aggregate performance.

Each aggregate also incurs a storage capacity overhead of approximately 7-11%, depending on the disk type. On systems with many aggregates this can result in lost storage capacity.

However, the overhead comes about due to additional block-checksumming on the disk level as well as usual file system overhead, similar to the overhead in file systems like NTFS or EXT3. Block checksumming helps to insure that data errors at the disk drive level do not result in data loss.

Data ONTAP 8.0 supports a new 64bit aggregate format, which increases the size limit to approximately 100TB (depending on storage platform) thus restoring the ability to configure large spindle counts to increase performance and storage efficiency. ([1])

Model history

This list may omit some models. Information taken from, and

Model Status Released CPU Main memory NVRAM Raw capacity Benchmark SPECsfs
FASServer 400 Discontinued Jan 1993 50 MHz Intel i486 ? MB 4 MB 14 GB ?
FASServer 450 Discontinued Jan 1994 50 MHz Intel i486 ? MB 4 MB 14 GB ?
FASServer 1300 Discontinued Jan 1994 50 MHz Intel i486 ? MB 4 MB 14 GB ?
FASServer 1400 Discontinued Jan 1994 50 MHz Intel i486 ? MB 4 MB 14 GB ?
FASServer Discontinued Jan 1995 50 MHz Intel i486 256 MB 4 MB ? GB 640
F330 Discontinued Sept 1995 90 MHz Intel Pentium 256 MB 8 MB 117 GB 1310
F220 Discontinued Feb 1996 75 MHz Intel Pentium 256 MB 8 MB ? GB 754
F540 Discontinued June 1996 275 MHz DEC Alpha 21064A 256 MB 8 MB ? GB 2230
F210 Discontinued May 1997 75 MHz Intel Pentium 256 MB 8 MB ? GB 1113
F230 Discontinued May 1997 90 MHz Intel Pentium 256 MB 8 MB ? GB 1610
F520 Discontinued May 1997 275 MHz DEC Alpha 21064A 256 MB 8 MB ? GB 2361
F630 Discontinued June 1997 500 MHz DEC Alpha 21164A 512 MB 32 MB ? GB 4328
F720 Discontinued Aug 1998 400 MHz DEC Alpha 21164A 256 MB 8 MB 464 GB 2691
F740 Discontinued Aug 1998 400 MHz DEC Alpha 21164A 512 MB 32 MB 928 GB 5095
F760 Discontinued Aug 1998 600 MHz DEC Alpha 21164A 1 GB 32 MB 1.39 TB 7750
F85 Discontinued Feb 2001 256 MB 64 MB 648 GB
F87 Discontinued Dec 2001 256 MB 64 MB 576 GB
F810 Discontinued Dec 2001 733 MHz Intel P3 Coppermine 512 MB 128 MB 1.5 TB 4967
F820 Discontinued Dec 2000 733 MHz Intel P3 Coppermine 1 GB 128 MB 3 TB 8350
F825 Discontinued Aug 2002 733 MHz Intel P3 Coppermine 1 GB 128 MB 3 TB 8062
F840 Discontinued Aug/Dec? 2000 733 MHz Intel P3 Coppermine 3 GB 128 MB 6 TB 11873
F880 Discontinued July 2001 Dual 733 MHz Intel P3 Coppermine 3 GB 128 MB 9 TB 17531
FAS920 Discontinued May 2004 2.0 GHz Intel P4 Xeon 2 GB 256 MB 7 TB 13460
FAS940 Discontinued Aug 2002 1.8 GHz Intel P4 Xeon 3 GB 256 MB 14 TB 17419
FAS960 Discontinued Aug 2002 Dual 2.2 GHz Intel P4 Xeon 6 GB 256 MB 28 TB 25135
FAS980 Discontinued Jan 2004 Dual 2.8 GHz Intel P4 Xeon MP 2 MB L3 8 GB 512 MB 50 TB 36036
FAS250 EOA 11/08 Jan 2004 600 MHz Broadcom BCM1250 dual core MIPS 512 MB 64 MB 4 TB
FAS270 EOA 11/08 Jan 2004 650 MHz Broadcom BCM1250 dual core MIPS 1 GB 128 MB 16 TB 13620*
FAS2020 June 2007 2.2 GHz Mobile Celeron 1 GB 128 MB 68 TB
FAS2040 Sept 2009 1.66 GHz Intel Xeon 4 GB 512 MB 136 TB
FAS2050 June 2007 2.2 GHz Mobile Celeron 2 GB 256 MB 104 TB 20027*
FAS2240 November 2011 1.66 GHz Intel Xeon 6 GB
FAS3020 EOA 4/09 May 2005 2.8 GHz Intel Xeon 2 GB 512 MB 84 TB 34089*
FAS3040 EOA 4/09 Feb 2007 Dual 2.4 GHz AMD Opteron 250 4 GB 512 MB 336 TB 60038*
FAS3050 Discontinued May 2005 Dual 2.8 GHz Intel Xeon 4 GB 512 MB 168 TB 47927*
FAS3070 EOA 4/09 Nov 2006 Dual 1.8 GHz AMD dual core Opteron 8 GB 512 MB 504 TB 85615*
FAS3140 EOA 2/12 June 2008 Single 2.4 GHz AMD Opteron Dual Core 2216 4 GB 512 MB 420 TB SFS2008 40109*
FAS3160 EOA 2/12 Dual 2.6 GHz AMD Opteron Dual Core 2218 8 GB 2 GB 672 TB SFS2008 60409*
FAS3170 EOA 2/12 June 2008 Dual 2.6 GHz AMD Opteron Dual Core 2218 16 GB 2 GB 840 TB SFS97_R1 137306*
FAS3210 Nov 2010 Dual 2.3 GHz Intel Xeon(tm) Processor (E5220) 8 GB 2 GB 480 TB SFS2008 64292
FAS3240 Nov 2010 Quad 2.33 GHz Intel Xeon(tm) Processor (Harpertown) 16 GB 2 GB 1,200 TB ?? ??
FAS3270 Nov 2010 Dual 3.0 GHz Intel Xeon(tm) Processor (E5240) 32 GB 4 GB 1,920 TB SFS2008 101183
FAS6030 EOA 6/09 Mar 2006 Dual 2.6 GHz AMD Opteron 32 GB 512 MB 840 TB SFS97_R1 100295*
FAS6040 Dec 2007 2.6 GHz AMD dual core Opteron 16 GB 512 MB 840 TB
FAS6070 EOA 6/09 Mar 2006 Quad 2.6 GHz AMD Opteron 64 GB 2 GB 1,008 TB 136048*
FAS6080 Dec 2007 4 to 8 2.6 GHz AMD dual core Opteron 64 GB 4 GB 1,176 TB SFS2008 120011*
FAS6080 SFS97_R1 164408*
FAS6210 Nov 2010 48 GB 8 GB 2,400 TB
FAS6240 Nov 2010 4x 2.53 GHz Intel Xeon(tm) Processor E5540 96 GB 8 GB 2,880 TB SFS2008 190675
FAS6280 Nov 2010 4x 2.93 GHz Intel Xeon(tm) Processor X5670 192 GB 8 GB 2,880 TB
Model Status Released CPU Main memory NVRAM Raw capacity Benchmark SPECsfs

Note: EOA = End of Availability

SPECsfs with "*" is clustered result. SPECsfs performed include SPECsfs93, SPECsfs97, SPECsfs97_R1 and SPECsfs2008. Note that results of different benchmark versions are not comparable. Check for more details.


External links

See also

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