Use HDD in multiple "cache" pool?


jebusfreek666

Recommended Posts

I know that you can use them, I am just wondering if my use case is a good idea or not? I want to use one as a location for my CCTV. I will have around 15 cams recording 1080p 24 hours a day. I want to write to a cache device so avoid the constant writes to the array. And since the largest SSD's are crazy expensive, I figured I could just throw a 6Tb HDD in there for this purpose. Then have mover run and put the videos on to the array overnight for storage. I would then have a script (I assume?) to remove files from the array when they reach 30 days old. So, basically I am wondering if the use of a HDD is better for this instance (or possibly 2 in raid 1) or would it be better to use multiple SSD in raid 0?

Link to comment
2 hours ago, jebusfreek666 said:

So, basically I am wondering if the use of a HDD is better for this instance (or possibly 2 in raid 1) or would it be better to use multiple SSD in raid 0?

It really would depend on your goal and the problem you are trying to fix and why not write directly to the Array ?

 

How much data/day are we talking about ?

A single HDD pool would only have slightly better write speed than the Array and no redundancy.

A RAID0 SSD pool will be faster than the other solution and the Array but still not provide redundancy. Still, you'll have more space than RAID1.

 

Are you looking for:

  • write speed
  • pool size
  • redundancy
  • limit the spin up time of the Array
  • something else
  • a mix of the above ?
Link to comment

yeah this is what i did also...

i didn't wan't the cameras constantly writing to my array, and i didn't want the recordings filling up my other cache drive.

 

i had a 1TB spinner, so configured a 1 slot pool device as a cache for my cctv recording.

i ended up leaving the share set to prefer, so the recordings are not being moved to the array. so at the moment there is no redundancy.

i figure it works the same as an unassigned disk, but i prefer that it is a native UNRAID function unlike unassigned devices which is a plugin.

 

i'll let it run a few weeks and see how much space I'll need for it then i'll assign it to only one disk in my array. i also wanted to see how data would need to be moved every day.

i have a feeling that it may not be viable to move all the recordings over to the array every night... so i'll probably make it a 2 disk pool for redundancy.

 

just curious, how many gigs does your 15 1080p cameras use every 24 hours?

Link to comment
2 hours ago, ChatNoir said:

Are you looking for:

  • write speed
  • pool size
  • redundancy
  • limit the spin up time of the Array
  • something else
  • a mix of the above ?

 

I guess pool size and redundancy would be the most important. I am not sure how important write speed is really in this instance, since NVRs routinely have used HDD. I am not sure on the exact size of drive I will need, but rough estimates have put it well over the 2Tb range daily unless I am doing this wrong. I could have it just write directly to the array, but I feel like this would be a waste as it would be writing not only the data but also dual parity 24/7. I thought it would be nice to have mirrored copies as a cache pool and then set it to move the files over while I slept. 

Link to comment
2 hours ago, limawaken said:

i'll let it run a few weeks and see how much space I'll need for it then i'll assign it to only one disk in my array. i also wanted to see how data would need to be moved every day.

i have a feeling that it may not be viable to move all the recordings over to the array every night... so i'll probably make it a 2 disk pool for redundancy.

 

just curious, how many gigs does your 15 1080p cameras use every 24 hours?

 

If you set it up to one of your array disks wont you just be right back in the situation of constant writes to the array? That's why I wanted to do a raid 1 cache pool, for redundancy. Depending on how much space 30 days worth of video used, I could just leave it on the HDDs I guess. But I only have a few spare 6Tb drives, and think it is going to be a lot more data than that. 

 

What do you mean it might not be viable to move to the array every night? Do you mean there would be too much data to transfer in that time span?

 

As for the total size used by my cams, I do not have this info yet. It will take a while before it is up and running. It is still sort of in the planning phase. 

Link to comment

because it is set up as a cache pool in unraid, you are able to configure the cache setting for the share. in my case it is currently set as "prefer".

cctv is configured to use this share, so the recordings are not being moved to the array.

later i might want to save the recordings to the array, then i will change the cache setting for my share to "yes", then during the day cameras will write the recordings onto the pool, at night mover will move the recordings over to the array. there won't be any constant writes to the array.

 

does that make sense? I'm sorry if i'm wrong. I'm just tinkering about, not an expert by any means!

Link to comment
38 minutes ago, limawaken said:

then i will change the cache setting for my share to "yes", then during the day cameras will write the recordings onto the pool, at night mover will move the recordings over to the array.

 

Yes, that is correct. I was wondering because in your previous response you said:

 

3 hours ago, limawaken said:

then i'll assign it to only one disk in my array.

 

Which I took to mean writing to a dedicated disk in the array.

Link to comment

when you configure the share you can select the share to exclude other disks so that it only writes data to one dedicated array disk (of course parity disk also spins up when mover is working).

also this would avoid other disks in the array spinning up when the cctv recordings are being viewed.

 

sorry i wasn't clear.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.