February 19, 20179 yr Hey guys looking for some performance tips on how to increase the speed of my unraid server. Been looking into a few different options and I wanted to get some opinions on the matter. Currently I run my VM's directly on the cache drive but have been notified that it could be better to use an unassigned device to run the VM's on. Only thing I'm worried about is not getting the speed of 4 raided ssd's on the VM itself. a max of 2 VM's are running at one time. 2(4) cpu cores have been assigned to unraid 2 cores and 2 hyperthreaded cores. I was thinking about purchasing an NVME pcie ssd for the VM's and removing them from the cache array. To hopefully decrease the load on the cache array for anyone transferring to and from the machine. And hopefully decrease the amount of time on the parity check. Currently it takes anywhere from 10-14 hours. Cores are isolated already Disk settings have been altered http://prntscr.com/eaksrp 4 Cache drives in raided btrfs array 2TB data drive has a btrfs filesystem 4 storage chipsets in total. 2 cache drives share 1 chipset. 2 cache drives have their own chipset, and the data and parity share chipsets.
February 19, 20179 yr I would not agree with the advice you got to run your vm's on an unassigned device... SSD is SSD and the cache drive is perfectly fit for running VM's on, there is no benefit in using a device outside the array. There -is- a possible negative: The cache drive is a core unraid function. Unassigned Devices is a plugin developped by a 3rd party, it is a perfectly fine product but it in basis it could run into trouble when unraid updates and/or changes. Running your VM's would seem like a very core thing to do which is why I prefer to run those functions on the most stable part of the setup, and that would exclude plugin functionality. You can simply use a folder on your cache drive and mark that share as "cache only". You can use a btrfs cache pool to increase redundancy, or even speed over a single SSD. I can basicaly only see advantages in using the cache drive over an unassigned device..
February 19, 20179 yr Author I would not agree with the advice you got to run your vm's on an unassigned device... SSD is SSD and the cache drive is perfectly fit for running VM's on, there is no benefit in using a device outside the array. There -is- a possible negative: The cache drive is a core unraid function. Unassigned Devices is a plugin developped by a 3rd party, it is a perfectly fine product but it in basis it could run into trouble when unraid updates and/or changes. Running your VM's would seem like a very core thing to do which is why I prefer to run those functions on the most stable part of the setup, and that would exclude plugin functionality. You can simply use a folder on your cache drive and mark that share as "cache only". You can use a btrfs cache pool to increase redundancy, or even speed over a single SSD. I can basicaly only see advantages in using the cache drive over an unassigned device.. So it doesn't seem to get much better than I currently have it setup at least for VM performance. And for overall system speed, the only way I'm going to increase performance is by swapping the data or parity drives for SSD's?
February 19, 20179 yr I would not agree with the advice you got to run your vm's on an unassigned device... SSD is SSD and the cache drive is perfectly fit for running VM's on, there is no benefit in using a device outside the array. There -is- a possible negative: The cache drive is a core unraid function. Unassigned Devices is a plugin developped by a 3rd party, it is a perfectly fine product but it in basis it could run into trouble when unraid updates and/or changes. Running your VM's would seem like a very core thing to do which is why I prefer to run those functions on the most stable part of the setup, and that would exclude plugin functionality. You can simply use a folder on your cache drive and mark that share as "cache only". You can use a btrfs cache pool to increase redundancy, or even speed over a single SSD. I can basicaly only see advantages in using the cache drive over an unassigned device.. So it doesn't seem to get much better than I currently have it setup at least for VM performance. And for overall system speed, the only way I'm going to increase performance is by swapping the data or parity drives for SSD's? Data and parity drives on SSD are a bad idea. The unraid system does not support trim.. Also there would be absolutely no benefit in write speed, write speed is bottlenecked by the unraid system that calculates and maintains partity, not by the speed of the parity drive. So: - data drives and parity drives as traditional drives - cache drive pool based on SSD - Keep all your VM's on the SSD's - Enable turbo writes to make the speed of your array as fast as possible - Rune tunetables_tester to figure out what specific settings are the optimum ones for -your- specific setup It's not going to get faster then that in a real scenario.. If you want to go to ridiculous scenario: - Do not use array drives, do not use parity - Do not use the array at all - Set a RAID BTRFS cache pool setup out of as much high capacity SSD drives as you can afford - Place all your data in the BTRFS cache pool Ofcourse you seriously increase the risk of data loss and are basicaly not using the unraid core functionality anymore.
February 19, 20179 yr And hopefully decrease the amount of time on the parity check. Currently it takes anywhere from 10-14 hours. None of your proposals will have any effect on this because cache is not part of the parity protected array.
February 19, 20179 yr And hopefully decrease the amount of time on the parity check. Currently it takes anywhere from 10-14 hours. Disks: 2TB Total Storage - 1 x WD Green 4TB (Parity) - 1 x WD Blue 2TB (Data) Parity check speed is strictly related to array drive speeds, in this case your 2 WD drives. If you want faster parity checks, you need faster and bigger spinners. In general, I've found that parity checks average 2 to 3 hours per terabyte, 2 hours if fast drives, 3 hours if slow drives.
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