Video content on internet has become more and more popular in the recent years. To deliver streaming video via internet requires huge storage for content, high network bandwidth and sufficient computing power. In addition space efficiency is also very important since many content delivery service providers deploy their edge nodes on ISP facilities that have limited real estate to be shared by the customer. Sun Storage 7000 Unified Storage Array from Sun Microsystems address these requirements all in one box. The storage appliance comes with an easy to use management tool, which makes it a perfect fit for content delivery applications.
We apply Sun Storage 7210 Storage Array (SS7210) to a streaming edge-node deployment case. With up to 91,500 hours of 1Mbps videos stored in the storage and using a number of streaming media servers for streaming the performance is outstanding for both striped and mirrored configurations. A SS7210 can deliver more than 735MB/s video streams, which is equivalent to delivering 5880 1Mbps streams concurrently.
SS7210 has many nice features suitable for streaming application. First it has 48x1TB disks and supports 4 storage configurations out of box: double parity RAID (32.2TB) , double parity RAID with wide stripes (32.6TB), mirrored (19.7TB), and striped (41.2TB). All configurations can be done easily with a web based tool.
To get a sense the storage capacity of SS7210, using striped configuration SS7210 can store 91,5000 hours of 1Mb/s videos, while in mirrored configuration it can store 43,775 hours of 1Mb/sec videos.
Another nice feature of SS7210 is its networking capability. SS7210 comes with 3 PCI-express slots. Adding 10G NICs it can be configured as NFS, CIFS and iSCSI network storage with high network bandwidth so that multiple streaming servers can share video stored in SS7210.
To understand how SS7210 can be used effectively in an internet edge deployment we run 26 copies of Wowza Media Streaming Server Pro 3.0.3 (a product of Wowza Media Systems) on thirteen SUN Fire X4150s. Each X4150 NFS mounts the ZFS pool that resides in SS7210. To reduce the number of client systems needed for our test we run two instances of Media Servers and two instances of load generators on each X4150. Each instance of load generator simulates the same number of streaming sessions throughout the testing period. Each load generator requests a randomly selected video and receives the streaming content from one of the media server via the loop-back connection. All systems are connected to a C300 switch made by Force 10 Networks.
We tested both striped and mirrored configurations. For both cases 54,000 streaming files are populated in the storage, each contains 45 minutes 1Mb/s video. The load generator simulates video simulates playing a randomly selected video, stop and play another repetitively.
Since SS7210 is building on Open Solaris, it comes with Zetabytes File System (ZFS). With ZFS prefetch, SS7210 can prefetch needed file blocks to memory. However there are a few factors to be considered. ZFS fetches 128KB/block. Fetching more blocks each read could reduce the disk busy percentage, but fetching too many blocks at once increase the response time, hence increase the likelihood that a NFS client will see the NFS mounted device busy. This problem becomes severe when the total number of streams is high. Media server usually also implements its own read ahead mechanism. For Wowza Media Server we configure each stream reader to read 128KB to its buffer each time and read ahead when it sends 64KB of the buffered content. Therefore as long as a limited number of blocks are prefetched to the memory the IO latency can be hidden. SS7210 has pre-configured ZFS prefetch parameters based on this understanding.
Our experiments show that using 26 media servers SS7210 can deliver 735MB/sec with 91.5% CPU utilized for stripped configuration. For mirrored configuration, using 22 media servers SS7210 can deliver 750MB/s with 96.6% CPU utilized. For both cases NFS client on X4150 becomes the bottleneck. For striped configuration, while SS7210 disks are 90% busy, the NFS client on X4150 sees the NFS mounted device 100% busy. The performance of either configuration is similar and both are great.
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Posted by Komik Videolar on April 07, 2009 at 01:50 PM PDT #