Video Surveillance Storage Part 2 - SD Cards vs SSD

Important considerations when evaluating short term storage options

In our first entry on video surveillance storage, we discussed long term storage options and considerations. This entry will look at the different technology considerations for those seeking shorter-term storage.

There are numerous situations when an integrator, remote monitoring company or end-user will need short term storage, typically a few days to a week of storage. In some cases this is because the cameras are being continuously monitored and any evidence of loss or a crime is found within minutes or hours, let alone days. In other cases, the surveillance solution includes long-term central storage, using distributed storage mainly as a fault-tolerance mechanism protecting against network failures and downtime. Many cameras and encoders offer SD cards as a solid-state solution, which provides reasonable storage capacities at moderate prices.

There are better solid state storage options than consumer SD cards

Flash memory actually comes in several variations differing in speed, reliability and cost.  SLC NAND flash memory is the high end of the flash variants, providing the most reliable storage available, with a high cost to match. This type of high reliability “industrial” flash memory makes up part of our patented hybrid storage discussed in part 1 of this blog series. Each memory cell in SLC NAND has a 10X longer lifetime than its cheaper sibling, MLC NAND.

MLC NAND flash fills out the middle and lower end of flash storage options with multiple variations within the MLC category. MLC NAND flash in the mid-range provides a good combination of speed and reliability without breaking the bank. The larger the capacity of flash storage, the fewer times a single memory cell is re-written. Thus, theoretically MLC flash storage with 10X the capacity of SLC flash will have about the same reliability for sequential-write applications (like storing video). Unfortunately, when MLC flash storage capacities go beyond a point, read/write latencies and errors also increase. Thus, MLC NAND flash is a good solution for applications requiring short-term storage. MLC NAND based solid state disks (SSDs) up to 256GB in capacity are now fairly common and have been shown to have good reliability.

The lowest tier of MLC NAND flash is used in most consumer SD cards. These types of low quality flash storage are not designed for applications that require gigabytes of data per hour to be written  24 hours/day. Though an SD card slot is a common choice on many surveillance cameras and encoders, reliability will be a serious issue if the SD card experiences continuous video writes. If the installer or end-user is not careful about her choice of consumer or professional SD cards (those that use higher end MLC NAND), premature media failure is inevitable.

VideoIQ’s new Rialto Analytic Bridge line simplifies the choice for the installer by providing built-in industrial SSD storage based on high quality MLC NAND, in 40GB or 160GB capacities. The Rialto provides a short-term storage solution needed by our customers with better reliability and capacity than SD card.

So, when considering long or short-term storage options, make sure you understand the different storage choices, what they deliver in terms of reliability and capacity, and when you should make trade-offs between cost and reliability.

To read our other posts on distributed storage and its benefits, follow the links below:

Distributed Storage Goes Mainstream, February 28, 2011

Scalability and Intelligent Distributed Storage, March 16, 2011