Data Into Storage

I uploaded a picture to Facebook, here is a my guess how a packet of the picture flies and lands.

• Packet is sent to Linux kernel
• Linux kernel handles it to network adapter driver
• Network adaptor sends packet to network, Packet goes through few routers or any other devices and  reaches server in Facebook data center.
• Server network adapter collects data and sends it HTTP server application.
• HTTP server application wants save this packet permanently, so the packet is sent back to server kernel to be written on a storage device.
• Packet is sent to Fibre Channel driver, Fibre Channel adapter use Fibre Channel protocol to wrappers SCSI write command which contains the packet. 
• Packet in SCSI command flies over SAN and arrives at a storage controller system
• Storage controller system ( may be a RAID controller ) finds out which hard disk to write the data and wrap the data with ATA command.
• ATA command is sent via SATA cable and received by hard disk controller
• Hard disk controller decodes SATA information and the encode packet with EDC+LPDC and write to hard disk. ( a lot of complexity is hidden in this step, that is the my current job ...  )

There is a lot of overhead and complexity here and there. 

Reference