IP Storage Solutions - iSCSI SANs & NAS Appliances

S
torage Area Networks or SANs are dedicated, independent networks that provide access to consolidated data storage typically in block level format. SANs are primarily used to make storage devices, generally data disk arrays and tape or disk libraries accessible to servers. These storage devices appear like locally attached devices to the operating systems that provision them for resource use and management. SANs, typically isolated to their own physical or virtual networks, are generally not accessible through the main local area network and must be accessed through drive allocation assigned by a server, server cluster or server farm.

Unlike Direct-Attached-Storage (DAS) found commonly in a typical server, Storage Area Networks increase storage capacity utilization dramatically. Through SANs, multiple servers utilize the various disk arrays that make up the SAN storage pool through the creation of virtual hard drives or LUNs. Each LUN or virtual drive maintains a dedicated file system local to that specific server. These specific virtual drives are "carved out" of the entire overall storage pool based on specific application requirements.

Virtual LUNs may utilize 1, 2, 3, or more drives depending on the specific spindle counts required. Spindle count is generally determined by application requirements like SQL, Exchange, SharePoint and others. An operating system LUN would not require the same amount of spindles (hard drive count) as would a typical SQL or Exchange LUN since the overall performance metric is much less stringent. Moreover, LUNs are typically created from "like" hard drive sizes and speeds and is recommended to never mix and match, as it could severely hamper system performance.

Storage Area Networks also offer additional benefits including the ability for servers to boot directly from the SAN itself; bypassing the need for any internal server storage requirements whatsoever. This not only allows for better storage management and cost savings by utilizing a single storage repository, but it also provides quick and easy replacement of faulty servers instantly. Direct access to the vacated LUN by the replacement server allows for immediate online availability.

Additionally, SANs also provide a more efficient and cost effective disaster recovery processes. Storage replication features from SAN to SAN allow for exact data de-duplication from site to site without distance limitations.

Popular protocols used for architecting Storage Area networks consist of iSCSI, Fibre Channel (FC) and Fibre Channel over Ethernet (FCoE). For the small and mid-sized business looking to implement a new storage area network, an iSCSI SAN is the integration method of choice for the SMB data storage environment.

iSCSI SAN Requirements:

iSCSI SAN Hardware Requirements

The only true recommended hardware requirement for implementing an iSCSI SAN is TCP/IP connectivity between the SAN storage pool and the Servers that will connect to it. Best practices implement a dedicated, high-speed network at the fastest possible speeds (Gigabit Ethernet - 10 Gigabit Ethernet) for best performance. This dedicated network can be of the physical or virtual nature by design. Today's high-end network switches support VLANs or Virtual LANs that can be used to segment your standard network data traffic from that of the Storage Area Network traffic. This best practice design would remove any possible latency / bandwidth issues that may arise from extensive network traffic of both TCP/IP and TCP/IP encapsulated within SCSI commands. Jumbo frame support also helps in the delivery of this block-level data, especially with I/O intensive applications.

iSCSI SAN Software Requirements

iSCSI SAN connectivity requires a special type of software. Both the SAN Storage Array and the directly attached servers (Windows, Linux or Apple) that are utilizing resources from the shared storage pool require this specialized software. The SAN Storage Array requires the iSCSI target software while the connected servers must run software known as an iSCSI initiator.

Utilizing Existing Server Network Interface Cards or Separate TCP Offload (TOE) Adapters

The standard, most common, as well as the most cost effective iSCSI implementation is utilizing the basic software iSCSI initiator. Within this standard implementation, the host CPU (onboard server cpu) provides all of the protocol handling functionality and processing power. While the most common, this is also the major culprit of under performing iSCSI SANs today.

A significant improvement over the standard and basic software iSCSI initiator is TCP/IP stack-offload, commonly known as TOE. The TCP offload engine (TOE) moves the TCP/IP stack processing to the onboard network controller. These TOE supported iSCSI SAN adapter cards provide the processing power for the intensive iSCSI protocol command sets, resulting in a zero performance hit from the onboard server CPUs and increasing the overall iSCSI SAN performance dramatically.

Network Attached Storage (NAS)

Network Attached Storage (NAS) is usually provided by a specific NAS storage appliance running a specific, stripped-down version of an operating system and supplying varying capacities and numbers of internal hard drives. NAS appliances are designed to provide file-based data storage services to other computers on the same local area network.

NAS data storage appliances generally contain one or more hard drives and are often split into logical, redundant storage arrays and utilize various RAID levels for performance and redundancy. Network-attached storage removes the file serving responsibility from other servers on the network. SMB, CIFS, NFS, and AFP are the typical protocols supported by such NAS appliances today. Typically, NAS appliances are much more affordable than an equally outfitted SAN due to the general design with file sharing support. They can range in price from small desktop-level NAS file sharing appliances targeted toward the consumer to enterprise-level, highly scalable storage solutions with incredible performance. These high end enterprise-level NAS appliances are capable of sustaining the intense read-write operations found in today's database and application driven programs like SQL, Exchange and SharePoint.

By overall design principles, the main difference between a NAS appliance and a Storage Area network is that a NAS appears to the client operating system as a file server. File servers are usually shared out drives that allow client computers to "map" or connect specific drive letters to locally served shares from the NAS appliance. Storage Area Networks appear to the client operating system (generally a server in this case) as a disk or set of disks, visible by server volume management tools or utilities.

Hybrid Storage Designs - As IP storage continues to evolve, certain organizations may need the file-level support that NAS appliances provide along with the block-level storage iSCSI SANs are known for. As a result, Hybrid Storage Solutions are quickly gaining popularity. A NAS Gateway allows network servers and client endpoints to access files over the LAN with the files stored directly on an iSCSI SAN storage array. The NAS Gateway acts as the interface between these file-level requests (NAS functionality) and the block-level storage provided by the SAN.

NAS Storage Appliances at a Glance:

NAS Appliances - An Inside Look

A NAS Appliance or NAS "Box" is a dedicated storage server that attaches directly to a common network via an ordinary ethernet connection (typically using gigabit ethernet or higher) with an assigned or DHCP provided IP Address. As storage requirements increase, Multiple NAS Appliances can be added to the LAN as needed. However, as more NAS appliances are deployed and more users connect to these storage servers, network bottlenecks and bandwidth saturation can put additional strain on oversubscribed ethernet LANs resulting in extensive network latency issues and slow access to available resources.

NAS Storage Capacity

In terms of shear storage capacity, NAS Appliances are capable of providing massive amounts of data storage compared to their SAN counterparts. 30TB, 60TB, 100TB and beyond are very common when utilizing 1-3TB SATA drive capacities. SATA drives are by far the most common type of drives found in today's NAS Storage Appliances. SATA drives allow for low-cost and high-density storage. SAS (Serial Attached SCSI) drives, because of their high-end performance capabilities, are becoming more commonly used in enterprise-level NAS models.

Most NAS Appliances include RAID support for data protection. Common RAID levels include RAID 0, RAID 1, RAID 5, RAID 6, RAID 10 and RAID 50. NAS systems also include varying amounts of onboard memory (RAM) to cache network data to and from the disk arrays.

Managing NAS Storage Appliances

NAS Storage Appliances generally run proprietary operating systems and are configured and managed using a standard Web browser. This also allows administrators to check status, diagnose issues and make changes on-the-fly to the NAS configuration from any workstation attached to the LAN.

NAS Appliances for Backup

NAS Appliances most always include backup / replication utilities as well as the ability to create point-in-time snapshots; found traditionally on higher-end, enterprise-level NAS systems.

Tighter backup windows, due to increasing storage capacities and the amount of data requiring consistent backup, are forcing administrators to move backup tasks to NAS Appliances. Disk-based backup storage is displacing tape as a backup medium due to its enhanced speed, RAID data protection features and cost-effectiveness. These features, combined with ease of installation, are making NAS devices attractive backup targets.

ISCSI Storage Area Networks (SANs) are frequently touted as the natural solution for small and mid-sized businesses (SMBs) moving to networked data storage. Due to the expensive nature of Fibre Channel SANs, iSCSI SANs offer the ability to use much of the existing network hardware already in place today.

IP data storage, now firmly established and entrenched as a viable alternative to 2Gb and 4Gb Fibre Channel SANs, is primed for incredible expansion as IP data storage devices leverage the performance and next-generation features embedded within today's 10 GbE technology and tomorrow's 40GbE / 100GbE networks. The capabilities of 10 GbE combine to greatly accelerate TCP/IP and iSCSI protocols by increasing data transfer throughput and I/O performance, which in turn, dramatically reduces network latency and CPU utilization.

Network Attached Storage (NAS) Appliances allow for incredible amounts of data to be stored at a lower cost than a SAN due to the specific file-serving nature that NAS Appliances provide. As a typical file serving device, NAS storage arrays can serve 100's of Terabytes of data using low-cost SATA hard drives. Multiple NAS Appliances can exist on the same local area network (LAN) since they attach directly using a standard Gigabit Ethernet connection.

As file storage demands grow, so to does the need to provide better, more efficient methods to maintain data within a central repository and avoid the typical "individualized" data silos present in most organizations today. Storage Area Networks and Network Attached Storage are two separate architectures that can effectively manage data storage requirements.

General iSCSI SAN Benefits:

  • Support for Existing Network / Server Hardware
  • Much more cost-effective than Fibre Channel SANs
  • Easily Scalable
  • Virtualization Support for an End-to-End Virtualized Solution
  • 10 Gigabit Ethernet Support and Beyond
  • Designed for I/O Intense Applications like SQL and Exchange
  • Great for Backup / DR with Thin Provisioning & Data Deduplication
  • Centralized Storage Pool for Easy Management

General NAS Benefits:

  • Easily Deployed using Standard Ethernet Connection
  • Massive Storage Capacities
  • File Serving Support - TCP/IP, NFS, CIFS, AFP
  • Disk Based Backup / DR
  • NAS Clustering
  • Virtual NAS Solutions
  • Easily Deployed as Cloud Storage

SAN and NAS solutions offer many benefits and advantages to meet your data storage requirements. Let The Go2IT Group assist you in planning these storage requirements. Learn more about your storage options and the solution that is best for you.

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