Makau Network Attached Storage Device (NAS)
Why Makau Uses the Network Attached Storage Device (NAS) for the Makau Education Library Appliance.
Makau looked at many devices before selecting the Network Attached Storage device as the preferred method of hosting the Makau Education Library. The NAS appliance provided us with the speed, reliability, availability, ease of installation, and relatively low cost necessary to service our customers' needs. Below is an explanation of the different types of storage architecture used today and we believe will clearly show why the NAS appliance is the best solution we could make available to our customers.
Storage Architecture - Connecting Storage to Your Network
There are 3 basic storage architectures available when connecting storage to your network. Direct Attach Storage (DAS), Network Attach Storage (NAS) and Storage Area Network (SAN). The following are definitions for each type of storage architecture
Direct Attach Storage (DAS)
Direct attach storage is the old way of doing things. DAS is storage connected directly to a file server via SCSI. With a direct attach storage system storage is local to a specific file server. This single server controls all information. Adding storage to your network using this model requires installing another network server with additional storage capacity. Another method might also entail bringing down an existing network server and installing additional storage devices into it, or connecting new storage devices to it via external cabling. Today's networks do not allow for the downtime required for this type of implementation.
Performance:
Direct Attach Storage is the slowest of all of the storage architectures. Attaching directly to storage servers means that processors in the server need to manage application requests and move data across the bus and monitor traffic on the network simultaneously. This creates too many demands on the network to provide quick access to attached storage.
Scalability:
Storage volume is tied to server capacity in DAS model. Adding storage requires server downtime, physical space in the server and in some cases new servers. Scalability is severely limited.
Availability:
Storage in the DAS model is also tied to server availability. If an individual server goes down, all of the attached storage becomes unavailable, leaving you without access to your data. The complexity of network server hardware and operating systems adds unnecessary failure points in your storage strategy.
Total Cost of Ownership (TCO):
Adding the cost of general purpose network servers to the cost of storage makes DAS one of the most expensive ways to add storage to your network.
Network Attached Storage (NAS)
The concept of Network Attach Storage is quite simple. NAS attaches special-purpose storage appliances to the LAN, which can be shared by application servers, workstations and PCs on the network. These appliances have only one job-file serving. NAS devices can be distributed across a large network and managed centrally to provide a common pool of storage that can be shared by multiple servers and clients, regardless of their file or operating system. This enables efficient allocation of storage, alleviating the problem of one server running out of storage while another may have more than needed. Unlike Storage Area Networks (SANs) implementation is simple and straightforward with Plug and Play compatibility. NAS appliances use standard file-system protocols, such as Network File System (NFS) and Common Internet File System (CIFS) for data sharing across multiple operating systems.
Performance:
While NAS is not quite as fast as the SAN, it is certainly much faster than DAS. NAS offers users dedicated file server appliances that provide fast access and high-availability storage to UNIX and Windows NT clients on a network. Data access time is fast because the system only serves files. Files are offloaded from the host to free CPU cycles for other cycles. Separating the storage from the server also increases network reliability.
Scalability:
NAS allows you to separate your storage capacity from your server capacity and with NAS companies add storage as needed. NAS products scale to multiple terabytes, and by offloading file serving to these devices, servers can support more users. But be sure to consider your future storage needs. As your requirements increase, large numbers of NAS devices can be difficult to manage. While small NAS devices are great for projects or workgroups, larger systems may be necessary for mainstream data storage.
Availability:
The simplicity of NAS makes it more reliable than traditional LAN file servers and eliminates many failures induced by complex hardware and operating systems. Because the NAS device communicates directly with the client, files remain available, in the event of network server downtime, thus increasing data availability.
Total Cost of Ownership (TCO):
Specialized for high-speed file serving, NAS devices are significantly less expensive than general-purpose network file servers. Servers across different operating systems can share access to NAS devices so that enterprises can save money on hardware, maintenance and administration by consolidating data on fewer devices in a central location.
Storage Area Network (SAN)
SANs are high-speed networks that enable the interconnection of heterogeneous systems and storage elements. SAN gateways deliver transparent performance that attaches devices across multiple interfaces while permitting each to deliver its full performance capability across the SAN network. By putting storage devices on a separate high-speed network via a SAN, data can be directly accessed by multiple servers, workstations and PCs and be managed as a centralized storage pool. SANs need the bandwidth of interconnects such as Fibre Channel for optimum performance, availability and scalability. But because TCP/IP does not run over Fibre Channel yet, some interim SAN implementations may use legacy networks such as Ethernet or FDDI. When IP on Fibre Channel becomes available, all control and data traffic for server backup will be offloaded from the LAN to the SAN. SAN implementation is very complex because of all of the interoperability issues that can arise. Some vendors are trying to make it easier by supplying a "SAN-in-a-box." Unlike NAS, installing a SAN is not a do-it-yourself project. One of SANs greatest challenges is interoperability. The goal is for UNIX, Windows NT and Netware servers to have access to the same storage and share the same data. Today users cannot freely mix and match devices from different vendors because there are different device-level formats for each operating system. Once operating systems adopt a common structure at the device level sharing devices will become easier. Despite current drawbacks, SANs do promise some relief for enterprise storage-level issues.
Performance:
SANs improve performance by relieving congested LANs of high volume data traffic generated by backups, large data migrations, business intelligence systems and digital video and audio applications. Storage response time is faster because Fibre Channel links can transfer data at 100MBps. The potential problems with interoperability SANs can be difficult to manage because all of its components are designed for maximum throughput.
Scalability:
Multi-channel SCSI controllers can only support a maximum of 30 devices, while a Fibre Channel fabric of interconnected switches can address thousands of ports. Bandwidth can be allocated on demand and network reconfigurations are relatively simple. SANs allow users to increase storage capacity or re-map department needs without bringing down the system and disrupting data access, as all the disks are centrally managed from one location.
Availability:
SANs allow distributed servers to access large, consolidated storage resources for data-intensive applications. Shared storage pools can be accessed by multiple systems. In SAN architecture, all servers can have direct access to all storage devices, allowing one server to provide fail-over protection for dozens of other servers.
Total Cost of Ownership (TCO):
By creating a central storage pool for the entire user community, SANs can lower total cost of ownership. Fewer administrators are required to manage the storage, management is centralized from a single management interface and storage can be purchased separate from servers. The cost of storage can be amortized over more servers and the storage can be dynamically allocated and reallocated for maximum capacity usage. Also, Fibre Channel's high-speed and low latency shortens backup and restore times, freeing LANs and WANs for business applications that improve productivity and enhance revenue.
Currently, SANs are more expensive to implement than NAS because of the investment required in Fibre Channel hubs, switches and Fibre Channel-to-SCSI bridges. However, the price gap between Fibre Channel and SCSI is narrowing and the larger the enterprise, the higher the return on the investment. Given the right set of management tools, enterprises can see a return on investment in approximately two to three years.