syrys Posted May 12, 2016 Share Posted May 12, 2016 Hey Guys, I just got into Unraid and literally just setup the drives the other day. I added 2 SSDs to my cache pool (1x 120GB Samsung 840 Pro, 1x 240GB samsung 850 Evo). So, after installing the 2 drives, and starting the raid, this is what my screen looks like (refer to attached image). Why does it say 180 GB? Shouldnt it say 360GB (120 + 240)? What am i doing wrong here? Any advice is appreciated. Cheers. Link to comment
syrys Posted May 12, 2016 Author Share Posted May 12, 2016 oops, forgot to attach image Please note: my parity isnt checked yet, as im copying over 15TB of data, i will check parity once everything is done copying. Also, i have the 12 drive license, so it shouldnt have anything to do with the license restrictions. Link to comment
gundamguy Posted May 12, 2016 Share Posted May 12, 2016 Hey Guys, I just got into Unraid and literally just setup the drives the other day. I added 2 SSDs to my cache pool (1x 120GB Samsung 840 Pro, 1x 240GB samsung 850 Evo). So, after installing the 2 drives, and starting the raid, this is what my screen looks like (refer to attached image). Why does it say 180 GB? Shouldnt it say 360GB (120 + 240)? What am i doing wrong here? Any advice is appreciated. Cheers. It's not 360GB because it's the default settings for cache pools is as a RAID 1 not RAID 0. The original point of adding BTRFS and cache pool capabilities was to add redundancy for cache drives so data sitting on the cache drive was protected from drive failure. You can change it to a RAID 0 pool if you want though. Link to comment
syrys Posted May 12, 2016 Author Share Posted May 12, 2016 Hey Guys, I just got into Unraid and literally just setup the drives the other day. I added 2 SSDs to my cache pool (1x 120GB Samsung 840 Pro, 1x 240GB samsung 850 Evo). So, after installing the 2 drives, and starting the raid, this is what my screen looks like (refer to attached image). Why does it say 180 GB? Shouldnt it say 360GB (120 + 240)? What am i doing wrong here? Any advice is appreciated. Cheers. It's not 360GB because it's the default settings for cache pools is as a RAID 1 not RAID 0. The original point of adding BTRFS and cache pool capabilities was to add redundancy for cache drives so data sitting on the cache drive was protected from drive failure. You can change it to a RAID 0 pool if you want though. Ah, that makes sense. Hmm, if its raid 1, then shouldnt it say 120GB though (size of the smallest drive)? Where would i change this Raid 1 -> Raid 0 setting? Also, out of curiosity. I plan on installing couple of VMs (windows) on this machine (which will run purely on the cache). I do like the Raid 1 Redundancy for the cache for the main data drive pool, but its not necessary for the VMs. Is there any way for me to add a seperate drive for the VMs that is outside of the main cache pool? Also, what happens if i add few drives to the cache pool while it remains in Raid 1. Say 2x 240GB SSDs and 2x 1TB Spinny Drives. What sort of a cache pool monstrosity would i get, and what sort of pool size would it be? Link to comment
gundamguy Posted May 12, 2016 Share Posted May 12, 2016 Hey Guys, I just got into Unraid and literally just setup the drives the other day. I added 2 SSDs to my cache pool (1x 120GB Samsung 840 Pro, 1x 240GB samsung 850 Evo). So, after installing the 2 drives, and starting the raid, this is what my screen looks like (refer to attached image). Why does it say 180 GB? Shouldnt it say 360GB (120 + 240)? What am i doing wrong here? Any advice is appreciated. Cheers. It's not 360GB because it's the default settings for cache pools is as a RAID 1 not RAID 0. The original point of adding BTRFS and cache pool capabilities was to add redundancy for cache drives so data sitting on the cache drive was protected from drive failure. You can change it to a RAID 0 pool if you want though. Ah, that makes sense. Hmm, if its raid 1, then shouldnt it say 120GB though (size of the smallest drive)? Where would i change this Raid 1 -> Raid 0 setting? Also, out of curiosity. I plan on installing couple of VMs (windows) on this machine (which will run purely on the cache). I do like the Raid 1 Redundancy for the cache for the main data drive pool, but its not necessary for the VMs. Is there any way for me to add a seperate drive for the VMs that is outside of the main cache pool? Also, what happens if i add few drives to the cache pool while it remains in Raid 1. Say 2x 240GB SSDs and 2x 1TB Spinny Drives. What sort of a cache pool monstrosity would i get, and what sort of pool size would it be? Good questions: Why it's not 120GB, because it's not a traditional RAID 1, it's BTRFS "RAID 1", and BTRFS does things a bit differently then standard RAID. You could add the disk in another way, possibly though the unassigned devices plugin. As far as I know there is no way to have a mix of cache pool and non-cache pool disks at this time... (intresting idea though...) You can change the command next to the button marked balance, then hit balance to run the balance command with the new settings to re-balance into another "BTRFS raid Level"... but this really isn't official supported. I'm not sure what will happen honestly... but this BTRFS space calculator might help. Link to comment
syrys Posted May 12, 2016 Author Share Posted May 12, 2016 Good questions: Why it's not 120GB, because it's not a traditional RAID 1, it's BTRFS "RAID 1", and BTRFS does things a bit differently then standard RAID. You could add the disk in another way, possibly though the unassigned devices plugin. As far as I know there is no way to have a mix of cache pool and non-cache pool disks at this time... (intresting idea though...) You can change the command next to the button marked balance, then hit balance to run the balance command with the new settings to re-balance into another "BTRFS raid Level"... but this really isn't official supported. I'm not sure what will happen honestly... but this BTRFS space calculator might help. i dont quite get the options in the calculator, but i will google around a bit and take your word for it. Either way though, if you have a 100gb drive and 200gb drive in btrfs and the drive pool states 150gb usable, then if you use all the 150 gb, and somehow lose the 200gb drive, then you would need some crazy sorcery or time travel to be able to get back the data (atleast the missing 50GB). So, i dont quite understand the logic of this btrfs thing. Has anyone tested this? So your cache pool is safe as long as your largest drive, and if that dies, then all is lost. Do you by any chance have a link to this "unassigned devices plugin"? i will google shortly, but incase if i end up with something old/incorrect might be a great if you have a link and if you know of it. If i want to pass through a separate HDD (one that is not in the raid/cache) to my VM, is this what you use? I was told in another thread that you can pass drives into your VM without having to have the drive as a part of the raid, i just wasent told how i do that. Link to comment
gundamguy Posted May 12, 2016 Share Posted May 12, 2016 i dont quite get the options in the calculator, but i will google around a bit and take your word for it. Either way though, if you have a 100gb drive and 200gb drive in btrfs and the drive pool states 150gb usable, then if you use all the 150 gb, and somehow lose the 200gb drive, then you would need some crazy sorcery or time travel to be able to get back the data (atleast the missing 50GB). So, i dont quite understand the logic of this btrfs thing. Has anyone tested this? So your cache pool is safe as long as your largest drive, and if that dies, then all is lost. Do you by any chance have a link to this "unassigned devices plugin"? i will google shortly, but incase if i end up with something old/incorrect might be a great if you have a link and if you know of it. If i want to pass through a separate HDD (one that is not in the raid/cache) to my VM, is this what you use? I was told in another thread that you can pass drives into your VM without having to have the drive as a part of the raid, i just wasent told how i do that. Link to Unassigned Devices. I'm not an expert on BTRFS but I think the real trick is that BTRFS stripes both data and metadata, by the default for BTRFS is Data = RAID 0 Metadata = RAID 1, for Unraid it's set as RAID 1, RAID 1, which might explain what it's doing... I don't think you can use that full 180 GB for data. Not really sure. I'm running with 2 equally sized cache disks so I don't really know. Link to comment
JorgeB Posted May 12, 2016 Share Posted May 12, 2016 Free space is incorrectly reported when using different size devices, it's a btrfs limitation, in your case you only be able to use 120GB. Link to comment
syrys Posted May 12, 2016 Author Share Posted May 12, 2016 @gundamguy, thanks for the link Free space is incorrectly reported when using different size devices, it's a btrfs limitation, in your case you only be able to use 120GB. So, what would happen if i plug in 2x 240gb ssds and 2x 1tb spinny drives and add them all to cache pool. What would i end up with? Link to comment
syrys Posted May 12, 2016 Author Share Posted May 12, 2016 So, what would happen if i plug in 2x 240gb ssds and 2x 1tb spinny drives and add them all to cache pool. What would i end up with? Actually, i feel this question deserves its own thread. Others might benefit from it, let me create one and i will link it here if any of you want to contribute. Link to comment
syrys Posted May 12, 2016 Author Share Posted May 12, 2016 Here's a link to the thread about cache pool speed and size: http://lime-technology.com/forum/index.php?topic=49047.0 Link to comment
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