Author Topic: The difference between SANs and NAS  (Read 4093 times)

Offline certforumz

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The difference between SANs and NAS
« on: October 17, 2010, 03:17:20 AM »
NAS grew out of the concept of file servers as a service to manage files for clients on a network. The file server approach achieved tremendous success through products such as NetWare and Microsoft Windows NT Server. With a file server in front, large amounts of storage could be hung from the server and served to users on a file-by-file basis. Management and backup of that data could be centralized off the server

SANs on the other hand, grew up around the concept of taking storage devices and storage-heavy traffic and creating a separate back-end network designed specifically for that type of traffic. Separating ownership of a server from its storage and placing all the storage devices directly on a Fibre Channel network allows a many-to-many connection from servers to storage, and from storage to other storage devices.

The Wires
--NAS uses TCP/IP Networks: Ethernet, FDDI, ATM (perhaps TCP/IP over Fibre Channel someday)
--SAN uses Fibre Channel

The Protocols
--NAS uses TCP/IP and NFS/CIFS/HTTP
--SAN uses E

http://www.nas-san.com/differ.html
http://www.networkworld.com/newsletters/stor/2000/1002stor1.html

Offline certforumz

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Re: The difference between SANs and NAS
« Reply #1 on: October 17, 2010, 03:21:00 AM »
NAS

Almost any machine that can connect to the LAN (or is interconnected to the LAN through a WAN) can use NFS, CIFS or HTTP protocol to connect to a NAS and share files.

 A NAS identifies data by file name and byte offsets, transfers file data or file meta-data (file's owner, permissions, creation data, etc.), and handles security, user authentication, file locking

 A NAS allows greater sharing of information especially between disparate operating systems such as Unix and NT.

 File System managed by NAS head unit

 Backups and mirrors (utilizing features like NetApp's Snapshots) are done on files, not blocks, for a savings in bandwidth and time. A Snapshot can be tiny compared to its source volume.

SAN

Only server class devices with SCSI Fibre Channel can connect to the SAN. The Fibre Channel of the SAN has a limit of around 10km at best

A SAN addresses data by disk block number and transfers raw disk blocks.File Sharing is operating system dependent and does not exist in many operating systems.

File System managed by servers

Backups and mirrors require a block by block copy, even if blocks are empty. A mirror machine must be equal to or greater in capacity compared to the source volume.
« Last Edit: October 17, 2010, 03:23:08 AM by certforumz »

Offline certforumz

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Virtualization
« Reply #2 on: October 17, 2010, 05:08:11 AM »
Three important types of virtualization:
 
  • network virtualization
  • storage virtualization
  • server virtualization

Network Virtualization:
  This is a method of combining the available resources in a network by splitting up the available bandwidth into channels, each of which is independent from the others, and each of which can be assigned (or reassigned) to a particular server or device in real time. The idea is that virtualization disguises the true complexity of the network by separating it into manageable parts, much like your partitioned hard drive makes it easier to manage your files.

Storage Virtualization: This is the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console. Storage virtualization is commonly used in storage area networks (SANs).

ServerVvirtualization: is the masking of server resources (including the number and identity of individual physical servers, processors, and operating systems) from server users. The intention is to spare the user from having to understand and manage complicated details of server resources while increasing resource sharing and utilization and maintaining the capacity to expand later.