General question, looking for observations.

If you have two HDDs in a DVR and one fails, can you simply remove the bad one and use the other while waiting for a replacement?

The more I reread that, the less likely it seems. Whaddaya think?

Thanks.

Do you need to save the video? Where is the configuration saved?

Kind of depends on the brand and model. Why do you need to wait for a replacement? Is it under warranty?

That would VERY much depend on the brand and model of the NVR and whether the drivers were set up as Raid 0 or Raid 1

Yep.
We need more info.

Model numbers and current set up configuration would help.

In 95% of DVRs/NVRs the answer would be yes.
OS, config, etc. reside on board.
HDDs are simply for storage.

Even if system is setup for RAID0 or 1, HDDs are allowed to be swapped.
Obviously you'll lose data depending on RAID type.

Now, if you got one of the PC based VMS with server type OS, you would treat that like a computer when it comes to HDD replacement.

I should mention that my above answer is in regards to CCTV DVRs, though most concepts would also be applicable to cable boxes and dish/directv DVRs.

In most cases you'd have to go to HDD config pagr and initialize/ reformat the harddrive.

^ This

Thanks. I am specifically asking about CCTV DVRs. (It's AMAZING how easy it is to leave out an important detail like that!)

...in most cases you'd have to go to the HDD config page and initialize/reformat...
the new drive you put in?
the remaining old drive you didn't take out, meaning you'd lose the info on that drive?


As to RAID0 or RAID1, when you have two hard drives just for the larger amount of storage you get with two drives, not because you want a double copy of everything (which I assume is what a RAID setting gives you), do you have to set it up as RAID anything?

You would need some kind of volume manager that combines those two physical drivers into one logical drive. Otherwise you couldn't freely write to them as if they are the sum of two drives. RAID will do that as will other schemes. Either way there is some way in the admin UI to tell the system to do that. But I have not looked at every DVR to know that they do this by default.

In most CCTV DVRs multiple harddrives are NOT set up in any RAID configuration.
They are simply meant to extend recording capacity.
And no, you can't really see what's recorded on which drive or what you'll lose once one of them fails.

Again, once you step up ro enterprise grade stuff with RAIDs, automatic data duplication and backup, things change.

Most home and small business (<64channels) CCTV DVRs are not mission critical and failed HDD simply gets replaced and life goes on.

Well, yeah, of course not. I was looking for general information. I didn't expect anyone to have looked at everything! Thanks for the input.


Taking that as the starting position, and it's logical to think it is,

...and when the failed HDD gets replaced, does the information on the still-good HDD get lost because somewhere there is, or was, a record of what's recorded on which drive?

It depends.
I've seen it go both ways.
I have seen where searching for events comes up with a list, however, when event is selected for playback no video is shown and error pops up.

I usually tell clients not to count on any data to be salvageable and initialize all hard drives.
If client balks at the idea of losing data, I quickly offer proper backup solutions with their associated costs and in ALL cases all of the sudden that data is no longer as critical as it was 60 seconds ago :-)

Hard drives just don't fail that often, so when it does happen, statistically speaking, there is low chance that something of worth happened during that period.
What I find more often is that hard drive died 6 months ago and no one bothered to investigate the flashing error on the screen or the beeping on the DVR. I get called because something did happen and now they wonder if there is any way to recover the recording. Again, mentioning the cost of data recovery by certified companies usually settles the matter.