Can you hear the drums beating?  If you listen closely, there has been some traffic on the technology grapevine lately and it has to do with digital video recorders (DVRs). In recent months, I have been hearing more and more comments directed at DVR maintenance and breakdowns, so I felt it was a good time to take a closer look.

I once heard someone refer to a DVR system as a PC on steroids. Although these products encountered some initial obstacles, such as high cost and buggy hardware, much of that has changed for the better. Even with newer technology, customers should be made aware that these systems need periodic attention, maintenance and repair. Can you say “Maintenance contracts?”

During the past couple of years, many dealers, technicians and customers have been excited about making the switch from tape-eating analog VCRs to smooth, highly reliable, solid-state digital DVRs. While it’s true we are making the transition, for some it may not be that smooth. However, with a better knowledge of DVR problem areas, we will all end up with happier techs and customers.

Heat Is the Prime Culprit in Failures

The No. 1 factor in DVR failures and trouble is heat. While the processors generate some of this heat, the main source are high speed, advanced technology attachment/integrated drive electronics (ATA/IDE) hard disc drives (HDD). (Note: ATA is the name given by the American National Standards Institute [ANSI] to the IDE interface.) ATA drives are now the most popular drives for DVRs due to their low storage cost and increased reliability.

Recently, I had a conversation with Geoff Thiel, technical director for DVR manufacturer PI Vision of Orlando, Fla.

When asked about HDD reliability, he stated, “First, HDD manufacturers are improving the reliability of ATA drives. Maxtor, for example, is offering MaXLine™ II for near-line applications. Put simply, these have the ATA interface of typical PC desktop drives, and the dependability and reliability of SCSI or fiber-channel drives that are more typically used in servers.”

Additionally, Thiel says, “With three-year warranty, five-year component design life and one million-hour MTTF, these new drives are a significant step forward. DVRs should move away from budget-priced desktop ATA drives”

3 Ways to Measure Temperature
DVR system heat is often referred to in three categories: core, ambient and environmental temperatures.

Core – Heat of the processor or HDD device. In HDD, it comes from the electronics and the drive motor/ spindle assembly. Temperature devices are built within the systems electronics to adjust and monitor.

Ambient – Area within the DVR and/or HDD enclosure. In a HDD, this is often referred to as the area within 1 inch of the spinning platters. If your system does not have a built-in temperature monitor, you can use an inexpensive indoor/outdoor electronic thermometer to monitor ambient temperature. This temperature is often mistaken for environmental temperature.

Environmental – Area in a room immediately next to the DVR. Since equipment cooling deals with airflow, this temperature will add to any heat being generated and circulated within the DVR.

This may seem very simple and basic, but poor heat management is the leading long-term killer of DVRs and other electronic equipment. If you have a room of 68° F, the ambient temperature of a DVR cabinet can shoot to 90° F or higher if it is not ventilated properly. Even if you have had systems running that hot where nothing major happened, it is just a matter of time until it does.

There are several goals to cooling a DVR system. One is to make the system more stable in its demanding, 24/7 operation. Another is to maximize your customer’s investment, which means having a happy customer!

First 90 Days Are the Most Dicey

So what about those 500,000+ hours of mean time between failure/mean time to failure (MTBF/MTTF) figures we see so much of? They are statistical figures and typically apply to perfect lab conditions.

If you want to look at how a HDD manufacturer is doing, a better number is the annual failure rate (AFR), which is a running average of failed units. (Caution: Some manufacturers reference AFR as annual field rate, which includes all returns.) This rate is typically less than 1 percent. Remember, this also includes HDDs that fail within the first 90 days when most are the result of shock in handling of the drives.

If you have made it past the first 90 days and can keep your ambient heat to less than a 20° F increase of the environmental heat level (68° F), you are doing your best to get maximum output from your DVR.
How much difference can a little bit of increased heat make on the life of a HDD? As a rule of thumb, every 10-percent increase above the 20° F differential we covered earlier can result in a 50-percent decrease in the reliability of the electronics.

Diagram 1, on page 22 of the January 2004 issue of Security Sales & Integration,  is from a HDD manufacturer and shows AFR vs. temperature on a 7,200 revolutions per minute (rpm) ATA drive. Notice the rapid increase after the 50°-60° C points (140° F). The goal is to keep it at the other end of the curve, at 40° C, which is still 104° F core temperature.

AC, Fans, Ventilation Among Keys

There are also some supplemental HDD cooling technologies you can implement. One is called a bay cooler, which is basically a bank of fans placed in an adjacent empty HDD bay slot or a thin fan blower assembly mounted right to the HDD chassis.

The following test results illustrate how a HDD fan can perform even better than a large enclosure fan. HDD case temperature without a fan was 115° F; case temperature with a case fan was 109° F; case temperature with a HDD cooler fan was 92° F.

Another type of cooling device is a heat-pipe system (see Diagram 2 on page 24 of the January 2004 issue of Security Sales & Integration). This device acts like a giant heat sink. I particularly like this method because it is quiet and energy efficient.

Some general tips to keep the temperature of a DVR down are:

Air conditioned or at least well-ventilated rooms.

Well-ventilated security cabinets (use large fans if possible).

Make sure replacement fans are not put in backwards.

Use HDD bay fan units or heat-pipe assemblies.

Provide spaces between multiple HDD units (don’t stack them together).

Secure internal cabling so airflow is not blocked in case.

Install additional cabinet fans.

Do a BTU inventory on larger DVR systems during site planning.

Don’t move desktop DVR units around on counter top while running.

Devices Continue to Get Smarter

Today’s HDD comes with a technology firmware called S.M.A.R.T. (self-monitoring analysis and reporting technology), which is designed to recognize conditions that indicate and provide sufficient warning of imminent drive failure. The firmware can give a warning but can’t predict a failure.

Additionally, some DVR manufacturers are writing sophisticated error-checking software that will help ignore errors in a video stream and automatically rebuild damaged files and directories.

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