WD Purple Questions

[TDC]

I'm preparing to purchase WD Purple HDDs for a Dahua NVR5208-8P-4KS2E for 8 IPC T3241T-ZAS cameras from Empire Andy.

I'm thinking of getting 8GB storage (1GB/camera) but am confused whether I need to get 2x4GB, 1x8GB, or 2x8GB for the DVR.

Also, what RPM and cache is recommended?

Thanks for any information! I didn't find the answer when reviewing the Cliff Notes.

 

[biggen]

I think you mean TB right?

Anyway, the specs show up to 10TB max for each drive and you can have two drives at most. RPM and cache shouldn't matter. 5400rpm should be a bit quieter and use less power.

 

[TDC]

Yes, thanks for the correction Biggen, I did mean TB.

Would I be good if I only purchased 1x8TB rather than 2x4TB? I'm assuming the 2 HDDs are for redundancy purposes in case one HDD fails but that's just a guess.

Thanks for the clarification regarding the RPM and cache.

 

[biggen]

The more hard drives you use, the greater the risk of drive failure. I'm not sure if the NVR supports any kind of RAID 1 array. Doesn't show it on the specs so I doubt it.

I'd just use one.

 

[TDC]

Very helpful Biggen - thanks again!

 

[Opeth]

The more hard drives you use, the greater the risk of drive failure. I'm not sure if the NVR supports any kind of RAID 1 array. Doesn't show it on the specs so I doubt it.

I'd just use one.

Please be kind and explain that...
It is better to use just 1 hard drive if the nvr has 2 an option and why is that? Because im planing on getting an nvr with 2 position of hard drive to store many days of recording

 

[samplenhold]

The more hard drives you use, the greater the risk of drive failure

Why? That makes no sense to me.

I have three 10TB drives in my BI server. I divide up the cams between them. Raid is worthless for surveillance cams. If the DVR will support 2 drives and up to 10TB, why would you not get two 10TB drives? That would give you the maximum retention period.

 

[SecuritySeeker]

The more hard drives you use, the greater the risk of drive failure.

Why? That makes no sense to me.

More components is more points of failure. So a system with two (identical) drives has a 2x greater risk of drive failure than a system with just one (unless this is setup in a redundant manner, eg RAID 1). With two separate drives you wouldn't have total data loss though but chances of losing (50% of your) data are indeed doubled. With a RAID 0 system the chance of total data loss (100%) due to drive failure is doubled.

With a 2 drive RAID 1 system the chance of a single hard drive failing is also doubled but the risk of failure of the entire RAID 1 system failing irrecoverably (meaning total data less by both drives failing) is reduced.

 

[weigle2]

Your model, NVR5208-8P-4KS2E, does not support raid at all. You would need at least an NVR that has a 4 HD capacity at the very least. Putting in 2 drives in yours, will give you more storage space. I have been running an NVR5216-4KS2 for years with no problems with drive failure, running 2 WD Purple 4TB drives. If you only have 1 drive, and it should fail, your NVR will be useless. At least with 2, if one dies, the NVR will still run but only record to the one drive until you replace the failed one.

 

[biggen]

More components is more points of failure. So a system with two (identical) drives has a 2x greater risk of drive failure than a system with just one (unless this is setup in a redundant manner, eg RAID 1). With two separate drives you wouldn't have total data loss though but chances of losing (50% of your) data are indeed doubled. With a RAID 0 system the chance of total data loss (100%) due to drive failure is doubled.

With a 2 drive RAID 1 system the chance of a single hard drive failing is also doubled but the risk of failure of the entire RAID 1 system failing irrecoverably (meaning total data less by both drives failing) is reduced.

This. This is the answer. More parts = more stuff to fail.

Every drive you add increases your chance of drive failure.

 

[samplenhold]

With that logic, I should only have one cam. Because if I have two, I have doubled the chances of having a cam failure. Oh my god! I have 18 cams. I am in big doo doo. I better get rid of cams before one fails!

 

[biggen]

With that logic, I should only have one cam. Because if I have two, I have doubled the chances of having a cam failure. Oh my god! I have 18 cams. I am in big doo doo. I better get rid of cams before one fails!

You are arguing data loss. I'm arguing drive failure. They are two different arguments. You are right (in your first post) in the fact that adding more drives will increase your resiliency to data loss (unless we are talking RAID 0) by divvying up your recordings amongst the various drives. In the case of two drives you will have 50% of the data in the event of a drive failure. But it doesn't get around the fact that you have DOUBLED your chance of drive failure by adding the second drive.

I run more than one drive in my BI installations as well and also divide them up. I said in an above post "I'd just use one" but I regret saying that to be honest. I'd take the increase in drive failure rate over the loss of storage space any day. Especially when its setup to divide up the camera recordings equally among the usable drives.

 

[SecuritySeeker]

With that logic, I should only have one cam. Because if I have two, I have doubled the chances of having a cam failure. Oh my god! I have 18 cams. I am in big doo doo. I better get rid of cams before one fails!

You're missing the point. You need to distinguish between component failure of a (sub) system (and a hard drive is a component of the overall system, just like a webcam is) versus system failure.

In a 2 drive RAID 0 configuration, failure of a single drive cause the whole system to fail and this has 2x the risk of system failure compared to a single drive.

With 2 separate drives failure of a single drive causes, in principle and provided the system can gracefully manage such an event, not system failure but you'll lose 50% or of your data. This is in no way worse than a 1 drive system (in fact you can argue it's better because you only lose 50% of your data but what you lose might be more or less random) and is also why adding more cameras is not a bad thing obviously (unless there's a chance the failure of 1 camera might lead to system failures somehow). This is what you are referring to.

In a 2 drive RAID 1 configuration you halve the chance of system failure due to drive failure.

Edit: Got Ninja'd by biggen

 

[Holbs]

side note.
I have owned a computer since the VIC-20 & Commodore 64 days (even a TRS-80 but that's showing my age).
I have never had a hard drive failure in all the PC's I have DIY built within 5-10 years of purchase. Anyone know the odds of hard drive failure of a new HD? I currently run a single 8TB Western Digital Purple in my Blue Iris PC. I could run a 2nd HD as RAID, but I do not worry if ever I get HD failure cause well... it's just video cam footage, not birth certificates or family pix or such. Could order a new one and have it arrive in 2-3 days so downtime would be at a minimum.

 

[biggen]

@Holbs I don't run RAID either for surveillance footage for myself. If it was for a bank or govt. entity or something similar it would be prudent.

Manufacturers post their MTBF but no odds that I've ever seen around. You can look at Backblaze's quarterly hard drive stats to see what failure rates they are seeing but those should be taken with very large grain of salt since those use cases aren't what you would expect for normal consumer loads.

Its the roll of the dice. Some drives last forever it seems. I have a few on the shelf that I'm looking at right now that are now only good for target practice.

 

[mat200]

side note.
I have owned a computer since the VIC-20 & Commodore 64 days (even a TRS-80 but that's showing my age).
I have never had a hard drive failure in all the PC's I have DIY built within 5-10 years of purchase. Anyone know the odds of hard drive failure of a new HD? I currently run a single 8TB Western Digital Purple in my Blue Iris PC. I could run a 2nd HD as RAID, but I do not worry if ever I get HD failure cause well... it's just video cam footage, not birth certificates or family pix or such. Could order a new one and have it arrive in 2-3 days so downtime would be at a minimum.

This should give you an idea, while stats are not for desktops - they do give you an idea.

Backblaze Hard Drive Stats Q1 2020

Hard Drive Failure Rates: A Look at Drive Reliability

We take a look at the Q1 2020 and lifetime performance of 129,764 hard drives used in the Backblaze data centers.

www.backblaze.com

note: I've seen numerous HDD failures... most often in laptops

 

[Old Timer]

My luck with WD Purple drives in NVR's over the last several years, I have had maybe 10% that fail by 5 years, and
most go longer then 10 years, you can just keep adding drives, or if you need more room, replace with a larger drive
and move them into a NAS unit for backup storage, or for Blue Iris.

Normal PC hard drives have a lot more failures in a NVR, and they last from 1 year to 5 years in continuous use.

 

[samplenhold]

I am sorry, but you are advising a Newbie that is purchasing an NVR for his cams at his home to only get ONE HDD because having TWO drives DOUBLES the chance of drive failure? That is ridiculous! This is not a data center.

Each drive has the same chance of failure whether there are one of two in the system.

 

[tigerwillow1]

In debating this 1 vs. 2 drive issue, does anybody know how the NVR handles 1 drive failing in a 2-drive system? There's a best case that it handles it gracefully, with the only downside being storage capacity is cut in half. There's a worst case where nothing at all is recorded. (I'm ignoring things like taking out the power supply, bursting into flames, etc.) Does the NVR somehow notify the user that a drive has failed, or does the user not even know of the failure? I don't think it's debatable that with 2 drives, the risk of a single failure doubles. There's a parallel to this with small aircraft. The risk of an engine failure with a twin is double the risk of an engine failure in a single. In a well designed twin with a pilot who knows how to handle the engine failure, the 2nd engine saves lives. In a poor-handling twin, or any where the pilot doesn't know how to handle the failure, continuing on a single engine leads to a high probability of a smoking hole with bodies in it. Does the NVR save data loss when a disk fails, or does it lead the user to a figurative smoking hole?

 

[looney2ns]

@TDC For a home NVR, your pocket book is the determining factor in how big or how many drives you purchase. Keep the box cool, install it in a conditioned space, don't block the air intakes or exhaust, clean the dirt out of it periodically, don't move it while it is powered on, and put it on a good backups and they will likely last a long, long time. Don't over think it.