deeks Posted January 24, 2020 Share Posted January 24, 2020 (edited) Hi guys, I would like to create a cache pool of 3ssd's of 480gb each in raid5 config. I have applied the -dconvert=raid5 -mconvert=raid1 command and expected about 960gb of free space using the carvox.org raid calulator. Unraid shows met 1,4Tb of free space howver. How do i know my raid setup is correct? Edited January 24, 2020 by deeks Quote Link to comment
JorgeB Posted January 25, 2020 Share Posted January 25, 2020 10 hours ago, deeks said: How do i know my raid setup is correct? You can check or post the output of btrfs fi usage -T /mnt/cache Note that for now when using raid5/6 with Unraid free space will be incorrectly reported, i.e., it doesn't account for parity, used space is correct, so say you have a raid5 pool using three 1TB devices with 500GB used, Unraid will report 500GB used and 2.5TB free when in reality you need to subtract space used by parity, so you have 1.5TB free. Quote Link to comment
deeks Posted January 25, 2020 Author Share Posted January 25, 2020 Hi Johnnie.black - thanks for your response. This is the output I get. : Linux 4.19.88-Unraid. Last login: Sat Jan 25 10:22:33 +0100 2020 on /dev/pts/0. root@unRaid:~# btrfs fi usage -T /mnt/cache WARNING: RAID56 detected, not implemented WARNING: RAID56 detected, not implemented WARNING: RAID56 detected, not implemented Overall: Device size: 1.31TiB Device allocated: 0.00B Device unallocated: 1.31TiB Device missing: 0.00B Used: 0.00B Free (estimated): 0.00B (min: 8.00EiB) Data ratio: 0.00 Metadata ratio: 0.00 Global reserve: 16.00MiB (used: 0.00B) Data Metadata System Id Path RAID5 RAID5 RAID5 Unallocated -- --------- --------- --------- -------- ----------- 1 /dev/sdc1 1.00GiB 512.00MiB 32.00MiB 445.60GiB 2 /dev/sde1 1.00GiB 512.00MiB 32.00MiB 445.60GiB 3 /dev/sdb1 1.00GiB 512.00MiB 32.00MiB 445.60GiB -- --------- --------- --------- -------- ----------- Total 2.00GiB 1.00GiB 64.00MiB 1.30TiB Used 768.00KiB 112.00KiB 16.00KiB I wiped the 3 cache disks so yes, used space is almost nil. But not getting a correct free space indication is a bit of a bummer as one might run out of free space without prior warning I suppose. Quote Link to comment
deeks Posted January 25, 2020 Author Share Posted January 25, 2020 I found link https://ohthehugemanatee.org/blog/2019/02/11/btrfs-out-of-space-emergency-response/ I gather that its a btrfs thing one has to live with Quote Link to comment
deeks Posted January 25, 2020 Author Share Posted January 25, 2020 In terms of raid setup, what are considerations for setting raid 5 for btrfs metadata and system volumes as well? Quote Link to comment
JorgeB Posted January 25, 2020 Share Posted January 25, 2020 13 hours ago, deeks said: -mconvert=raid1 You metadata is raid5, not raid1 like you said you did, I recommend using raid1 for metadata, it's much safer. Quote Link to comment
deeks Posted January 25, 2020 Author Share Posted January 25, 2020 yeah I tinkered around a bit with the mconvert last night...will revert to raid 1 😀 Quote Link to comment
deeks Posted January 25, 2020 Author Share Posted January 25, 2020 So with the raid5 setup I do need to check usage in stead of free space more than anything for my cache disks. Thanks for helping out! What I do still wonder is why my previous cache disk setup (2 ssd in raid1) did not start moving data to disk as it ran out of disk space. My cache folders were set to "prefer" in the share settings. I would have thought that Unraid woud not further fill the cache pool a a certain point. It didn't.... Quote Link to comment
JorgeB Posted January 25, 2020 Share Posted January 25, 2020 2 minutes ago, deeks said: My cache folders were set to "prefer" in the share settings. Prefer moves from array to cache, you want cache="yes". Quote Link to comment
deeks Posted January 25, 2020 Author Share Posted January 25, 2020 got it - thanks for that! Quote Link to comment
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