August 21, 20205 yr Hi, I've been thinking of building a multi disc cache pool for extra storage seeing that it can accommodate up to 24 drives. I'm running 6.8.2, and I'm just wondering if somebody has already done this, and how safe is it, what raid level would you use and are the cache drives "covered" by the parity drive ? Would you lose whatever is on that cache pool, if a disc failed ? Cheers
August 21, 20205 yr I setup in 16bay main case ( array pool ) + 12 and 13 bay external enclosure, enclosure always power off and disk RAID00 pool(s) usually group 4 disk per pool. 23 minutes ago, GeoffH said: cache drives "covered" by the parity drive ? Only array pool will cover by parity. Edited August 21, 20205 yr by Benson
August 21, 20205 yr Author 41 minutes ago, Benson said: I setup in 16bay main case ( array pool ) + 12 and 13 bay external enclosure, enclosure always power off and disk RAID00 pool(s) usually group 4 disk per pool. Thanks for reply, but not sure how you set this up... What do you mean by:- enclosure always power off and RAID00 pools in group 4 disk per pool. How do you create separate pools in cache ? I don't understand, sorry.
August 21, 20205 yr 5 hours ago, GeoffH said: How do you create separate pools in cache ? I don't understand, sorry. Multiple cache pools can be created manually (in conjunction with Unassigned Devices). See quoted post from Johnnie below. 6.9.0 (currently beta25) has multi-pool functionality built into the GUI so if you don't mind running beta then that will be more user-friendly. Note that any SSD formatted in 6.9.0 will NOT be backward-compatible to 6.8.x. Major point: avoid RAID-0 with HDD. That is strictly in the "do it if you know exactly what you are doing" category or you are asking for troubles. Also avoid BTRFS RAID-5/6 with HDD as well (ZFS RAID-Z1/2 is a better option for HDD). FAQ link
August 21, 20205 yr 7 hours ago, GeoffH said: Thanks for reply, but not sure how you set this up... What do you mean by:- enclosure always power off and RAID00 pools in group 4 disk per pool. How do you create separate pools in cache ? I don't understand, sorry. I misunderstood your questions, you ask multiple disk in cache pool, but I reply multi pool. BTW, if pool many disk together, even it is safe, but if you need maintenance it, i.e. replace one of fault disk, then you need spend lot of times, or you will got really slow performance. You may ref. below user case, for a 3 disks RAID-1 https://medium.com/@7sevens/btrfs-uneven-raid1-in-action-84e224c4af10 For my setting, due to those pools were outside array and haven't link with it. So if I don't need access them, I will power off it. If need them, just power on and mount them. Edited August 21, 20205 yr by Benson
August 21, 20205 yr Author 13 minutes ago, Benson said: I misunderstood your questions, you ask multiple disk in cache pool, but I reply multi pool. BTW, if pool many disk together, even it is safe, but if you need maintenance it, i.e. replace one of fault disk, then you need spend lot of times, or you will got really slow performance. You may ref. below user case, for a 3 disks RAID-1 https://medium.com/@7sevens/btrfs-uneven-raid1-in-action-84e224c4af10 For my setting, due to those pools were outside array and haven't link with it. So if I don't need access them, I will power off it. If need them, just power on and mount them. Hi, that's interesting..so lets see if I now understand.....you have a "cache pool" of 12 & 13 disks (have I got that right ?). And when you don't want them, you turn off the external enclosure(s). Have you had any disk errors when you turn them back on ?? If a disk failed, would you lose the data that was on the cache pool ??
August 21, 20205 yr 1 hour ago, GeoffH said: you have a "cache pool" of 12 & 13 disks (have I got that right ?). Those are standalone pool not link with array or cache pool, I usually form a pool by 4 disks, so a 12 bay will have 3 pool. You can decide how many disk in a pool or what RAID-level. The purpose mainly group smaller size disk to form a big storage, it also provide performance but not protection. 1 hour ago, GeoffH said: Have you had any disk errors when you turn them back on ?? So far no problem. 1 hour ago, GeoffH said: If a disk failed, would you lose the data that was on the cache pool ?? Yes, those are backup or temp data, I can lost it. Edited August 21, 20205 yr by Benson
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