February 9, 20179 yr So I'm trying to do as much learning about unRaid before I spend time setting it up on my machine and wasting SSD write cycles. Watching a spaceinvader1 video on Youtube, I finally grasp the relationship between the parity, data, and cache drives. But I'm trying to use unRaid as Linus did and create 2 gamers 1 PC. I understand how to pass through all the hardware to the two VMs correctly, but I'm wondering if I can set up the storage in an unconventional way for unRaid. I don't want to involve cache or parity if possible. I'd like to have 2 RAID1s set up. One with two data 1TB HDDs, and one with 2 smaller HDDs or SSDs for my 2 VMs' OSs. I would then split the data and smaller drives into two partitions so that each VM has half the small and half the data. Both the VMs' OS and Data half of the disk would be safe due to each having it's own individual RAID1 companion drive. I hope that makes sense. TLDR 4 drives. 2 Raid1s. Is this possible in unRaid?
February 9, 20179 yr Indirectly, yes. Because of the way parity works, if you assign 1 drive to parity and 1 to the first data slot, they will be a RAID1 set. As soon as you add another data slot, that no longer applies. Again, it's not REALLY a RAID1, but it acts that way anyway. Any writes to the data drive will be written identically to the parity drive. Reads will not be interleaved, they will all occur from the single data drive. The default configuration for the cache pool is RAID1, so there is your second SSD RAID1. I know you said you don't want to use parity or cache, but if you assign 2 identical drives to Parity and Disk1, and 2 identical drives to cache, you will be getting 2 RAID1 pools like you want. Assign 2 equal sized vdisks from each pool to each VM, and there you go.
February 9, 20179 yr Author Indirectly, yes. Because of the way parity works, if you assign 1 drive to parity and 1 to the first data slot, they will be a RAID1 set. As soon as you add another data slot, that no longer applies. Again, it's not REALLY a RAID1, but it acts that way anyway. Any writes to the data drive will be written identically to the parity drive. Reads will not be interleaved, they will all occur from the single data drive. The default configuration for the cache pool is RAID1, so there is your second SSD RAID1. I know you said you don't want to use parity or cache, but if you assign 2 identical drives to Parity and Disk1, and 2 identical drives to cache, you will be getting 2 RAID1 pools like you want. Assign 2 equal sized vdisks from each pool to each VM, and there you go. Ok. That makes sense. But my understanding is that unRaid will copy data from the cache drives to the data, and as a result of that, to the parity drive as well. Because the only point of the cache drives is to temporarily provide faster storage for the real Raid array being the data and parity drive. Is that correct? I don't want the cache and data disks to interact at all. I want the partitions made from those for each VM to show up on the VMs as different disks. SSD for OS and HDD for games.
February 9, 20179 yr But my understanding is that unRaid will copy data from the cache drives to the data, and as a result of that, to the parity drive as well. That is determined by the share settings. There are settings for leaving the data alone and not moving it.
February 9, 20179 yr Community Expert Indirectly, yes. Because of the way parity works, if you assign 1 drive to parity and 1 to the first data slot, they will be a RAID1 set. As soon as you add another data slot, that no longer applies. Again, it's not REALLY a RAID1, but it acts that way anyway. Any writes to the data drive will be written identically to the parity drive. Reads will not be interleaved, they will all occur from the single data drive. The default configuration for the cache pool is RAID1, so there is your second SSD RAID1. I know you said you don't want to use parity or cache, but if you assign 2 identical drives to Parity and Disk1, and 2 identical drives to cache, you will be getting 2 RAID1 pools like you want. Assign 2 equal sized vdisks from each pool to each VM, and there you go. Ok. That makes sense. But my understanding is that unRaid will copy data from the cache drives to the data, and as a result of that, to the parity drive as well. Because the only point of the cache drives is to temporarily provide faster storage for the real Raid array being the data and parity drive. Is that correct? I don't want the cache and data disks to interact at all. I want the partitions made from those for each VM to show up on the VMs as different disks. SSD for OS and HDD for games. No, not correct. Each user share has settings for how and whether it uses cache. If you want a user share to remain on cache you can set it to cache-only. If you want a user share to not use cache you can leave it at the default setting, which is cache-no. All this probably only makes sense after you understand user shares, so you may need to do some more reading. Basically, the user shares are the aggregate of all top level folders from cache and array disks. This is how the user shares are able to span disks.
February 9, 20179 yr Author Ok. Thank you. Sounds like it is possible. I'll look around and try to get a better grasp of user shares to keep the RAID1s independent.
February 9, 20179 yr Author I'm assuming unRaid doesn't care if I also use HDDs in the cache in case I don't wanna splurge more $$$ into this project?
February 9, 20179 yr Community Expert I'm assuming unRaid doesn't care if I also use HDDs in the cache in case I don't wanna splurge more $$$ into this project? You should be using your SSDs in the cache pool and your HDDs in the array. If you mix SSDs and HDDs in the cache pool you will not get SSD performance so in that case why use SSDs at all?
February 9, 20179 yr I'm assuming unRaid doesn't care if I also use HDDs in the cache in case I don't wanna splurge more $$$ into this project? Either spinners or SSD's will work, however VM performance will be pretty bad with spinners.
February 9, 20179 yr Author I wouldn't mix SSDs and HDDs. It would be all HDDs. I guess speed would be more of an issue than I thought. HDD as OS drive in regular computer is already super slow, I suppose the speed would be theoretically halved with 2 VMs. Thanks for the advice.
February 9, 20179 yr I wouldn't mix SSDs and HDDs. It would be all HDDs. I guess speed would be more of an issue than I thought. HDD as OS drive in regular computer is already super slow, I suppose the speed would be theoretically halved with 2 VMs. Thanks for the advice. HDDs for the cache (pool) is fine if all you want to do is cache writes to the array or run Dockers that aren't performance sensitive. Since you want to run VMs, though, you'll want SSDs.
February 9, 20179 yr Author Okay. I have a 500GB SSD in a different machine with almost no content in it. I'll toss that in as the cache drive for now. Can I add another 500GB SSD later for the redundancy? Or do they have to go in and be set up at the same time.
February 9, 20179 yr Community Expert Can I add another 500GB SSD later for the redundancy? YES See V6 FAQ sticky at top of this subforum for more about cache pool.
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