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Fibre Channel (FC) SAN
Block and file access unite with multiprotocol storage
By Greg Schulz
What you will learn from this tip: This tip looks at the pros and cons, as well as when and where to deploy multiprotocol storage, which is also referred to as "unified" storage.
Multiprotocol has been used to describe support for two or more networking interconnects or interfaces, for example Fibre Channel (FC) and Ethernet along with multiple protocols, including SCSI_FCP (FCP), iSCSI and FC-SB2 (FICON) among others. Other examples of multiprotocol include Fibre Channel over IP (FCIP) and Internet FCP (iFCP), used for enabling FC to span distances via IP networks.
Over the past few years, storage systems have adopted the multiprotocol model supporting tiered storage access with multiple connectivity interfaces and protocols supporting both file- and block-based access of storage. For example, network attached storage (NAS) offerings have evolved to support both NFS and CIFS along with other TCP-based protocols, including HTTP and FTP. More recently, some NAS products have further evolved to support iSCSI over Ethernet, network interface traditionally used for NFS or CIFS. Some NAS products have further evolved to support additional physical interfaces, including FC with FCP or TCP over InfiniBand.
Multiprotocol storage is also referred to as "unified" storage providing both block- and file-based access along with other functionality or packaging. For example, some packages that combine FC switches, iSCSI to FC bridges, NAS gateways, storage systems, management software and host adapters have, in the past, been called a "SAN in a can" or solution bundle. A differentiator of unified storage systems is how integrated the multifunction capability is. For example, is it via packaging multiple components together as a bundle? Or, is the functionality actually integrated via hardware and software?
Traditional block-based storage systems continue to evolve supporting interfaces, including FC with FCP or FICON for zOS IBM mainframes, Ethernet with iSCSI for IP-based block access, SCSI over InfiniBand, SAS or SATA. Some block-based packages have also added NAS support via a blade, attached processor or gateway for block- and file-based access. Another example of unified storage is a single system that supports multiple tiers of storage, combining high performance FC or SAS disk drives with large-capacity, low-cost FC near-line or SATA disk drives.
Another buzzword that has been used to refer to unified or multiprotocol storage is federated storage or in the case of Hewlett-Packard Co.'s (HP): All-in-One storage. Longtime NAS vendor Network Appliance Inc. (NetApp) has also entered the multifunction, multiprotocol storage game targeted at small and midsized business (SMB) environments with its StoreVault solution, while adapting its midmarket and enterprise NAS offerings to support block-based storage access using iSCSI and FC.
Another example of unified storage is the Microsoft Windows Unified Data Storage Server 2003 (WUDSS)-based Dell PowerVault NX1950 combining NAS and iSCSI target and initiator capabilities with Windows-based management capabilities.
Multiprotocol support today can be as simple as attaching an iSCSI or NAS gateway to an existing block-based storage system. This is a quick way for vendors to get packages into the marketplace. With the continued adoption of iSCSI, traditional block storage vendors, like EMC, have added native support (no bridge or gateway needed) to some of their storage solutions in addition to Fibre Channel support for block-based access.
The advantage of multifunction, multiprotocol unified storage is the ability to adapt to various customer application requirements and needs. Systems that combine block- and file-based access via iSCSI or FC and NAS are well suited for general purpose environments to consolidate storage and storage management functions or where a dedicated block- or file-based system is not required. Smaller environments, including branch offices, SMBs and small office or home office (SOHO) environments with general purpose storage needs benefit from the ease of use and multifunction capabilities of unified storage.
Additional benefits of unified or multifunctioned storage include:
- Native support to eliminate the need for managing an extra component along with eliminating a point of potential failure.
- Flexibility to align the right type of storage with the applicable access method (tiered storage access) to the application and service requirements.
- Easy to acquire, install and use with wizards and GUIs for common storage functions, including provisioning and remote administration.
- Similar to some NAS offerings, unified storage solutions may also support print functions to reduce the number of servers.
The flexibility of scalable unified storage can provide future proof and redeployment capabilities to maximize IT spending. On the other hand, some unified storage offerings trade scalability for ease of use and multifunction capabilities, similar to a multifunction copier. The down side is that when you out grow the capacity of the scaling capabilities, you either need to add another one or migrate to a different technology. Consequently, look for a system that can scale to meet your current and future storage capacity, performance and availability needs, or one that can coexist under common management with additional storage systems.
Caveats of unified or multifunctioned storage include:
- Limited scaling capabilities of smaller all inclusive storage appliances.
- Performance that may be compromised in favor of ease of use or functionality.
- Some functionality that may be an either/or situation, meaning NFS or CIFS; or iSCSI or FC; or block or file; however, not both at the same time.
- Determines which operating systems and applications are supported by the solution.
General things to keep in mind regarding unified storage include what management and storage software tools are included. For example, is local and remote mirroring or data replication included along with snapshots, data migration and general purpose configuration and management tools. Check to see if there are any hidden fees for activating and using the different protocols and functional capabilities.
About the author: Greg Schulz is founder and senior analyst with the IT infrastructure analyst and consulting firm StorageIO Group. Greg is also the author and illustrator of Resilient Storage Networks (Elsevier) and has contributed material to Storage magazine and other TechTarget venues.
24 Jan 2007
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