Standard HDDs in Raid 10 as cache drive? Multiple cache pools?


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As I'm researching my new build, I am still trying to wrap my head around how I will have a "working drive" or scratch disk. Ideally I'd have multiple terabytes for this purpose, and I'd love to not longer have an external attached to my desktop.

 

I have been searching and reading a ton of threads on the forums, but I still don't have a clear picture of what's possible. I know most people use a SSD (or multiple) as a cache drive and that technically multiple raid levels are possible. So at first I thought I might have a few SSDs as my cache, access this on the server through 10GbE, and just make due with less space. However I am now wondering if I could use 4 7200rpm HDDs in Raid 10 and my "scratch disk" that I access on the server via 10GbE. Does anyone run something like this? Is there a reason to not do this?

 

Also, if that is possible, is it also possible to run a second cache pool of a SSD (or multiple) to server as intermediary?

 

At the very minimum, I'll install an additional 1-2TB SSD in my desktop and use that as a scratch disk, and keep my unraid config fairly standard, but I'd love more space that's also fairly speedy, so I'm looking at my options.

 

Thanks!

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5 hours ago, johnnie.black said:

HDD RAID10 pool will perform better than a single HDD, it should perform somewhat below twice the performance of a single disk.

 

ZFS plugin allows you to have one (or more) ZFS pools outside the array or cache, they can't be used there.

 

For the 4 7200rpm drives that I have (Toshiba X300), is Raid 10 my best bet then? Previously I have had them in a G-Speed Studio thunderbolt 2 enclosure in Raid 5. That gave me 450-500MB/s read and write speeds. That would be my ideal performance.

 

So basically if I used the plugin, I would see the ZFS array as a separate, but accessible volume within UnRaid (and managed by)? Ideally I'd like to have my UnRaid array that I keep most data on and could keep growing. Then I could also have a high performance array that I could work from (6-12TB). Bonus would be a SSD cache intermediary. I am 100% okay and understand that it won't be a part of the UnRaid array.

 

Am I understanding this correctly?

 

 

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4 hours ago, andyps said:

For the 4 7200rpm drives that I have (Toshiba X300), is Raid 10 my best bet then? Previously I have had them in a G-Speed Studio thunderbolt 2 enclosure in Raid 5. That gave me 450-500MB/s read and write speeds. That would be my ideal performance.

 

Cache pool supports RAID5 but btrfs RAID5 is still experimental and not stable for production use.

 

4 hours ago, andyps said:

So basically if I used the plugin, I would see the ZFS array as a separate, but accessible volume within UnRaid (and managed by)? Ideally I'd like to have my UnRaid array that I keep most data on and could keep growing. Then I could also have a high performance array that I could work from (6-12TB). Bonus would be a SSD cache intermediary. I am 100% okay and understand that it won't be a part of the UnRaid array.

 

ZFS pool is not controlled by unRAID, you'd need to use the CLI.

 

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44 minutes ago, johnnie.black said:

 

Cache pool supports RAID5 but btrfs RAID5 is still experimental and not stable for production use.

 

 

ZFS pool is not controlled by unRAID, you'd need to use the CLI.

 

 

So I'd want to go with Raid 10 for my cache pool then. Am I able to have multiple cache pools, or am I limited to the one?

 

To clarify on the ZFS pool. That would not be controlled/created by unRAID, but would it be seen by unRAID? and accessible through the network and to the various VMs and things in dockers, etc? Would it just show up to unRAID as a volume? Is there an advantage to doing it that way, vs setting up a hardware raid 5 and bringing that in as an unassigned volume/drive?

 

Thanks for the info and patience with the questions!

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28 minutes ago, andyps said:

Am I able to have multiple cache pools, or am I limited to the one?

 

One

 

28 minutes ago, andyps said:

and accessible through the network and to the various VMs and things in dockers, etc?

 

Yes, it just won't show up in the GUI

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19 hours ago, johnnie.black said:

 

One

 

 

Yes, it just won't show up in the GUI

 

So if it's not the unRAID array or the cache drive, the only way for it to show up in the GUI is with the unassigned devices plugin? I could utilize a hardware raid as a volume or have multiple SSDs through that plugin. I will spend more time trying to find people who have been successful with hardware raids. Thanks for the info.

 

15 hours ago, 1812 said:

Post in this thread and maybe @limetech will consider implementing multiple cache pools someday!

 

 

 

Very cool! I will post in there as well. That would be a great feature. Thanks for the heads up.

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2 hours ago, andyps said:

So if it's not the unRAID array or the cache drive, the only way for it to show up in the GUI is with the unassigned devices plugin?

 

UD plugin can't mount or manage ZFS pools, like I said before you'll need to use the console to manage it.

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35 minutes ago, johnnie.black said:

 

UD plugin can't mount or manage ZFS pools, like I said before you'll need to use the console to manage it.

 

Sorry, yes I understand that now about ZFS. I was speaking to a hardware Raid 5 array or a Raid 10 array and passing it through the UD plugin. Not a part of the array or managed by unRAID, but able to be seen and shared. 

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14 minutes ago, andyps said:

 

Sorry, yes I understand that now about ZFS. I was speaking to a hardware Raid 5 array or a Raid 10 array and passing it through the UD plugin. Not a part of the array or managed by unRAID, but able to be seen and shared. 

 

As long as unRAID detects the hardware RAID as a single disk it shouldn't be a problem.

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