Hello all, excellent discussion.
So as regards John's comments, and Harolds, and Carl (!!!), the amount of time that it takes to fill one single hard drive of 4TB size will depend on the throughput of the cameras. We all agree on that. Now, COLDSTORE has a throughput limitation of 320 Mb/s, but that is total and is comprised of writing and reading. When building a system to work with Genetec (as with the system we have at AT&T Stadium here in Dallas), we usually match the Genetec server specifications which means that you have about 200 or so Mb/s of traffic being written to any individual COLDSTORE.
To a great degree the math is on our side here. For example, 50 cameras at 3.00 Mb/s running 24 hours per day, 7 days per week generates 150 Mb/s and will fill up 53.5TB in 30 days. That means 1.78TB per day, or one pair of 4TB drives every 2.24 days. In that case, on Monday, Tuesday and a quarter of Wednesday any drive data you need will be on a spinning drive, and from 75% of Wednesday on you would be pulling drive data from a drive that was powered off. If the fact that this can take 8 to 20 seconds to power that drive on, coupled with the seek time of the VMS, is too long for you then we would agree that COLDSTORE is not the right system to fit the needs.
However, if the benefits we do bring to the table- 10% of the power of the "average" RAID system, the ability to use any drive you wish, greatly reduced initial costs and operating costs, etc. outweigh the above then we are the right system to use.
The comment about drives being "on" then "off" over and over is not quite right either. The average COLDSTORE drive is turned off about 88% of the time and you can see that via the math above. Over the 30 days above, drives 1 and 2 are on for 2.2 days then off for 27.8. So, drives 1 and 2 are turned on at the beginning, run for 2.2 days, then off for 27.8, then on again, etc. 12 times per year- which of course does not account for the read cycles. Of course, for the average user, data is retrieved less than 5% of the time…so where is the “on and off” to which Harold refers? For the non-average user I could see more duty cycles, but for the average user that 5% figure holds true and it means that any given drive in a COLDSTORE has a far, far greater chance of being used for writing and then turned off until the next write cycle than constantly used for read and write. The most stressful part of a disk’s life is NOT being turned on and off; it’s constantly reading and writing that creates the wear and tear, fragmentation, etc. that kills the drive and requires folks to use RAID to protect data against disk failure. Do we not often turn off and on devices with hard drives such as our computers, our cable TV boxes, etc. with far more frequency?
If an end user did find themselves in a situation where constant read was a requirement, and they were concerned about the on off issue, then COLDSTORE allows you to pull the drive and read all of the data independently of the COLDSTORE. This is accomplished via DISKPLAY. So, you can take the original drive data, copy it, and then use the copy while preserving the original.
John, you are both right and wrong on data redundancy. We provide full redundancy during the write cycle with the mirrored write to overlapping disks. It is true that only one copy of the data is left behind once you step from Disks 1 and 2 to Disks 2 and 3; however, COLDSTORE cannot suffer a “RAID failure” that costs all of the data across all drives and due to the fact that it is likely that data on any given drive is not going to be retrieved, for most of the users of COLDSTORE that one copy is more than sufficient. In the event that an end user wants more than one copy of drive data, then it is more cost effective to use 2 COLDSTORE, each writing the same data, that it is to use any flavor of RAID system…for most! Carl and some folks are perfectly capable of designing a RAID system that has the same general per-TB cost as COLDSTORE (although the ease of use and power savings benefits would be hard if not impossible to match) but Carl and folks like Carl are not the average. We look to provide storage to customers who have long (30+ days) archive times and a large camera count (large being somewhat subjective).
I’ll close with this- COLDSTORE is certainly a radical departure from the “storage normal” and not for everyone. We do have limitations- we do not do general data, and we have integrations to a limited number of VMS partners (fortunately we cover some biggies with Genetec and with Milestone via Arcus and it is important to note that COLDSTORE was certified by Genetec for use with Security Center) and for some, the comfort of RAID is just not something we can overcome! We do have a whole lot of very satisfied customers around North America and the world, and for them COLDSTORE is the perfect solution for their needs.