RAID - Stripe vs Block Size for CCTV

[Steve21]

Good Morning All,

 

Getting a new CCTV server put in, and just wondering if anyone had any thoughts about stripe/block sizes. Reading online most people seem to leave them at 64kb but seeing it's all going to be large video files wouldn't it make more sense to put some nice chunky stripes/blocks in?

 

Will probably be RAID10 (or 6) if that changes anything in your eyes

 

Thanks,

Steve

[mavhc]

Surprised people would use RAID for CCTV, does it matter than much if 1 in 1000 times footage that, 999999 in 1000000 times is never viewed, is inaccessible?

 

Less stress on the drives if one writes continuously for x minutes, then has a rest as the next one writes.

 

But larger stripes would be better in general.

[Norphy]

Surprised people would use RAID for CCTV, does it matter than much if 1 in 1000 times footage that, 999999 in 1000000 times is never viewed, is inaccessible?

 

Less stress on the drives if one writes continuously for x minutes, then has a rest as the next one writes.

 

But larger stripes would be better in general.

 

Two reasons that I can think of:

 

1) It might not matter 99 times out of 100, but that one time it does matter, it really matters. I wouldn't want to be the one to explain to the authorities that our CCTV recorder missed recording a serious assault because of a drive failure and using RAID or similar mitigates that.

2) It's more convenient to store stuff on a single large contiguous volume than it is to scatter it across 4/12/24/36/48 drives. You might not want to use hardware/software RAID, you might want to use something like ZFS or Storage Spaces to combine the drives but the end result is the same.

[mavhc]

Also halves the amount of stuff you can record for the same money, it's a trade off

 

"The CCTV footage is too low quality" "The FPS were too low" "The video was deleted because it was >x days old"

[Norphy]

Also halves the amount of stuff you can record for the same money, it's a trade off

 

"The CCTV footage is too low quality" "The FPS were too low" "The video was deleted because it was >x days old"

 

Yes, it's a trade off. Everything is. You trade capacity against redundancy against resiliency against performance. Use RAID 10? Lose half your capacity. Use RAID 6? Slow write performance. Use RAID 5? Risk loosing the array entirely if a disk fails. Use JBOD/RAID 0? Lose the entire array when a single disk fails. Don't use any kind of RAID/storage combination technology? Risk losing an entire disks worth of footage which may be required at a critical juncture.

 

There is no right or wrong answer, everything depends on circumstances but given the potential risks, I would personally recommend using RAID of some description.

[EddyAllen]

Honestly I'd avoid RAID5 like the plague when it comes to CCTV. The amount of parity writes your going to have to be doing on continuous or even motion detection recording will be absolutely horrific, possibly even to the point of significantly reducing the lifespan of the array.

 

To my mind CCTV is something that when you need to use it in anger it HAS to be reliable. For that reason I would always RAID1 / RAID 10 a CCTV system. A lot of insurance companies quote based on the fact that you have operational CCTV and you don't want to be in a situation where you find you've got inaccessible footage due to a dodgy array.

 

What CCTV Software are you using as this will have an impact on your stripe size. Some software just continuously writes to a single active file and then starts on a new one every 500MB or so. Others store them in smaller chunks.