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Technology > The AVFS > The AVFS explained |
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What is different compared to NAS? Let's take a quick look at how AVFS accelerates network attached storage with iSCSI. A Windows, Mac or Linux client accesses an AVFS solution over standard Ethernet wiring and switches. The only moving parts of an AVFS solution are: 1. AVFS software installed on the client. 2. A storage server which maintains the file system and handles the AVFS protocol and file system and provides the storage. The AVFS protocol explained NAS is fundamentally slower than iSCSI due to the chatty nature of high level NAS protocol handling. iSCSI operates over the same Ethernet infrastructure and is a fast and efficient data transfer protocol. The combination of iSCSI for fast data transfers, and NAS for file system protocol awareness is used in the AVFS protocol to make a NAS system run faster. The following diagram shows how this works for a typical file access. The NAS system is burdened by metadata protocol overhead for each data transfer. In comparison, the AVFS protocol incurs protocol overhead only at the beginning of each file access. After that initial handshake, data transfers run quickly and efficiently over iSCSI. Because AVFS can transfer more file data over a shorter period of time, AVFS has a performance advantage over traditional NAS access. Large benefit in CPU utilization AVFS is not only faster than NAS, it is more efficient. NAS protocol handshakes between NAS clients and an NAS server consumes a lot of CPU cycles. Switching to the AVFS protocol reduces the burden on NAS clients (approx 7x less) and the storage server (12x less). As a result, more clients can share the same storage system and more CPU cycles remain for applications. Now what does this mean for professional Video, Film and Audio users? NAS disadvantages in professional Video, Film and Audio Table 1 shows a list of video and film formats in use today. This table by no means is complete but it certainly shows the large spread in bandwidth going from MPEG-2 video to 4K for film. Today almost all companies have a standard Gigabit Ethernet (GbE) network installed. The maximum theoretical bandwidth then between two network nodes is 125 MByte/sec. Using NAS normally a datarate of about 30 MByte/sec is obtained. According to the table such datarate looks okay when a number of compressed video formats are considered. However due to inefficiencies in NAS protocols a powerful storage server is required to accommodate even a limited number of clients with compressed video streams. This increases storage server costs. On the desktop a considerable percentage of CPU time is needed to handle NAS based communication. This limits the number of video streams/layers available to a desktop. Also often a latency is felt when using transport controls and scrub. Traditional SAN in a professional Video, Film and Audio environment To overcome these bottlenecks AV and Film companies who can afford this use SAN based solutions. As explained before in a traditional SAN system there is a separate data and communication path (see figure 3) with Fibrechannel for the data and Ethernet TCP/IP for the communication path. Handling two completely different network infrastructures is difficult. To make matters worse often an additional server is needed to handle the metadata traffic via the communication channel. So here we are with a Fibrechannel network, an Ethernet network, a storage server and a metadata server. For many pro Video, Film and Audio companies such a set up is too expensive and complicated to install, operate and maintain. Any failure in such a set up to quickly identify a problem requires highly qualified technical personel which is not always available. Continue to > The DDP & AVFS: superior shared storage solutions. |
 
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