5 messages, 4 authors, 2021-05-12 · open the first message on its own page
From: d tbsky <hidden>
Date: 2021-05-07 01:12:20
Adam Goryachev [off-list ref]
I guess it depends on your definition of raid 10... In my experience it means one or more raid 1 arrays combine with raid 0, so if each raid 1 arrays had 2 members, then it is either 2, 4, 6, etc for the total number of drives.
indeed. What I want to use is linux raid10 which can be used on 2,3,4,5, etc of disk drives. so it is unlike hardware raid 10.
From: Wols Lists <hidden>
Date: 2021-05-07 09:48:12
On 07/05/21 02:12, d tbsky wrote:
Adam Goryachev [off-list ref]quoted
I guess it depends on your definition of raid 10... In my experience it means one or more raid 1 arrays combine with raid 0, so if each raid 1 arrays had 2 members, then it is either 2, 4, 6, etc for the total number of drives.indeed. What I want to use is linux raid10 which can be used on 2,3,4,5, etc of disk drives. so it is unlike hardware raid 10.
If you're worried about losing two drives, okay it's more disk space, but add the third drive and go for three copies. Then adding the fourth drive will give you extra space. Not the best but heigh ho. Or make sure you've got a spare drive configured, so if one drive fails the array will rebuild immediately, and your window of danger is minimised. Cheers, Wol
From: Phil Turmel <hidden>
Date: 2021-05-11 00:26:51
On 5/7/21 5:46 AM, Wols Lists wrote:
On 07/05/21 02:12, d tbsky wrote:quoted
Adam Goryachev [off-list ref]quoted
I guess it depends on your definition of raid 10... In my experience it means one or more raid 1 arrays combine with raid 0, so if each raid 1 arrays had 2 members, then it is either 2, 4, 6, etc for the total number of drives.indeed. What I want to use is linux raid10 which can be used on 2,3,4,5, etc of disk drives. so it is unlike hardware raid 10.If you're worried about losing two drives, okay it's more disk space, but add the third drive and go for three copies. Then adding the fourth drive will give you extra space. Not the best but heigh ho. Or make sure you've got a spare drive configured, so if one drive fails the array will rebuild immediately, and your window of danger is minimised. Cheers, Wol
I do this for my medium-speed read-mostly tasks. Raid10,n3 across 4 or 5 disks gives me redundancy comparable to raid6 (lose any two) without the CPU load of parity and syndrome calculations. Phil
From: David T-G <hidden>
Date: 2021-05-12 18:55:06
Phil, et al -- ...and then Phil Turmel said... % % I do this for my medium-speed read-mostly tasks. Raid10,n3 across 4 % or 5 disks gives me redundancy comparable to raid6 (lose any two) % without the CPU load of parity and syndrome calculations. I've been reading and I still need to catch up on the notation, but how much space do you get in the end? I'm hoping to grow our disk farm and end up with 8+ disks. I'm more than a bit nervous about RAID5 across a bunch of 6T (or bigger) disks, so I've been thinking of RAID6. That would give me 6x6 = 36T plus two parity. Putting 8 disks in RAID10 should give me 6x4 = 24T with mirroring. That's a pretty hefty space penalty :-( But ... How does RAID10 across 5 disks as above 1) work and 2) work out? If you had 8 disks with a huge need for space, how would y'all lay out everything? % % Phil Thanks in advance :-) :-D -- David T-G See http://justpickone.org/davidtg/email/ See http://justpickone.org/davidtg/tofu.txt
From: Phil Turmel <hidden>
Date: 2021-05-12 18:55:06
On 5/12/21 1:27 PM, David T-G wrote:
Phil, et al -- ...and then Phil Turmel said... % % I do this for my medium-speed read-mostly tasks. Raid10,n3 across 4 % or 5 disks gives me redundancy comparable to raid6 (lose any two) % without the CPU load of parity and syndrome calculations. I've been reading and I still need to catch up on the notation, but how much space do you get in the end?
One third of the total, since I'm using n3.
I'm hoping to grow our disk farm and end up with 8+ disks. I'm more than a bit nervous about RAID5 across a bunch of 6T (or bigger) disks, so I've been thinking of RAID6. That would give me 6x6 = 36T plus two parity. Putting 8 disks in RAID10 should give me 6x4 = 24T with mirroring. That's a pretty hefty space penalty :-( But ...
I wouldn't use only two copies, as you cannot lose any two. With three copies, 8x6T/3 = 16T usable space. Heftier space penalty, but necessary to have confidence surviving a rebuild after a disk replacement.
How does RAID10 across 5 disks as above 1) work and 2) work out?
1) Linux raid 10 does not layer raid 1 on top of raid 0, but implements "n" copies of each chunk striped across all devices. Which is why the number of devices doesn't have to be a multiple of "n".
If you had 8 disks with a huge need for space, how would y'all lay out everything?
raid6. I pretty much always layer LVM on top of mdraid.
Thanks in advance :-) :-D
Phil