Video Editing over Gigabit EthernetCentralized Digital Video Storage

Currently at Malaspina video projects are stored on the hard drives locally, if students or employees want to work at a different editing station they can't access their projects unless we move them manually using an external Firewire drive. Often the suite a project was started on will not be available when the group is. I hope to create a system of storing projects in a central location where it can be accessed from any of our suites.

To accomplish this we are planning on using an Apple Xserve running Mac OS X Server connected to the workstations running Mac OS X with 1 Gbps Gigabit Ethernet using a dedicated Gigabit switch. We could use 2 Gbps Fiber Channel for increased network speed but the cost of host bus adapters, cables, switches and specialized SAN software (such as Xsan and ImageSAN) is prohibitive compared to cost of Gigabit Ethernet (which comes standard in Apple Xserves, PowerMac G4s and G5s.) Accounts could be located on the Xserve and projects stored in the user's Movies directory.

This sort of setup should accommodate up to four SD video editing suites simultaneously or perhaps two HD video editing suites (which we have no current plans for but I will provide data for interest sake.) Gigabit Ethernet is rated at a maximum of 125 MBps, although in reality users may achieve only 60 MBps to 70 MBps due to network overhead. Standard Definition video compressed for DV is roughly 3.5 MBps. DV compressed HD video (DVCPRO HD) requires roughly 12.5 MBps of bandwidth for realtime playback. To provide enough bandwidth for editing you should multiply its bandwidth requirement by a minimum of 2 (7 MBps is the highest amount of bandwidth that one iMovie station could generate in my single workstation tests). Using that math SD video editors will require 28 MBps (3.5 * 2 * 4 workstations) and one HD video editor will require 25 MBps (12.5*2) which fits into our 60 MBps to 70 MBps achievable bandwidth with Gigabit Ethernet.

I believe the real issue will be internal bandwidth (sustained disk read/write) on the server. The G5 Xserve with a single SATA hard drive for video will only give us about 25 MBps sustainable read/write, way too slow for four simultaneous editing suites but should be able to handle two effectively. If we add a PCI Hardware RAID card and 2 more SATA hard drives it should increase performance to roughly 50 MBps sustainable read/write allowing up to five clients to edit video simultaneously.

Another issue is the Xserves currently have a maximum storage capacity of 750 GB, this sounds like tons of storrage but you never know how your needs will grow. Especially since there would be no redundancy to the data. That means if one of the 3 drives used in the 750 GB RAID were to have a problem all students in all the suites would loose all there projects. This is unexceptable. Capacity, performance and redundancy could be increased with the addition of one or more Apple Xserve Raids (up to 200 MBps read/write with a maximum storage capacity of 3500 GB per unit.) Steve Mullen has a great article on the Xserve Raid and it's real world performance at Video Systems Magazine.

I have connected the 4 workstations to the Gigabit switch which is connected to the Xserve's second Ethernet adapter. The Primary ethernet adapter is connected to the College's 10/100 mb LAN. I then set up Mac OS X Server to share it's network from the primary Ethernet to the secondary port. Later I will tackle the daunting task of setting up workstation authentication through the Xserve

I've had some experience setting up Mac OS X servers before but if I run into problems I know were I can find Help. Now if I can incorporate this system of server storage of projects with template accounts and Windows account login I will be a very happy video tech.