Originally posted by Britoid
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Btrfs Working On RAID1 Round-Robin Read Balancing
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Originally posted by cynic View PostRAID is not intended for avoiding losing data. The tool for that purpouse is backup.
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With a classic raid 1 you have double the chance of data corruption compared to a single device.
(Meta)data-Instances or -specimens = 2 would be a better word at describing RAID1 or RAID10 in BTRFS.
And RAID5 would be instances=1 and parities=1 , RAID6 instances=1, parities=2
Such a change would hopefully had people understand that BTRFS' "RAID" is not RAID!!!
http://www.dirtcellar.net
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Originally posted by cynic View Post
RAID is not intended for avoiding losing data. The tool for that purpouse is backup.
Originally posted by cynic View PostAnyway btrfs is much better than "classical" RAID when it comes to preventing losing data.
In a normal RAID1 (or 10), If one of the copies of the data gets corrupted, the data is lost (because you cannot tell which copy is the the good one).
In btrfs, being it checksummed, you can detect and fix the corrupted copy.
With a classic raid 1 you have double the chance of data corruption compared to a single device.
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Originally posted by cynic View PostRAID is not intended for avoiding losing data. The tool for that purpouse is backup.
This is just a school-exam mantra. How do you "backup" data fsynced right now from ACID-compliant RDBMS?
Anyway btrfs is much better than "classical" RAID when it comes to preventing losing data.
In a normal RAID1 (or 10), If one of the copies of the data gets corrupted, the data is lost (because you cannot tell which copy is the the good one).
Of course I can. T10 Data Integrity Field ("fat" sectors), dm-integrity, crypto-authenticated data.
In btrfs, being it checksummed, you can detect and fix the corrupted copy.
Unless you set chattr +C or used nodatacow to have more performance than 10 year old USB drive.
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Originally posted by cynic View Post
if you have 4 drives in btrfs you can configure them in raid10 or raid1.
Since the redundacy level is always 2 copies, you get the same space.
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Originally posted by microcode View Post
Rarely matters. They call it raid1 in the config for familiarity but it really is just mirroring. It is also a more complex thing on btrfs than on block device RAID (where the block addresses are the same for everything).
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Since we're talking about what cooks everyone's noodle -- what cooks my noodle is that I had to do a double take reading that RAID1 Mirroring is "striped", I understand the usage is figuratively to indicate a "block" -- but in the other RAID topologies the data is quite literally striped -- in RAID 1 -- maybe I am mistaken but it quite literally is not AFAIK.
Edit: As it's been pointed out earlier, even though some of us use RAID1 to mitigate potential mechanical drive failures, it's not a backup in the same way that Snapshots are not a backup. Offsite backup with snapshotting, and cold storage are important to incorporate into data safeguarding.Last edited by ElectricPrism; 16 December 2024, 04:58 AM.
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Originally posted by cynic View Post
RAID is not intended for avoiding losing data. The tool for that purpouse is backup.
Anyway btrfs is much better than "classical" RAID when it comes to preventing losing data.
In a normal RAID1 (or 10), If one of the copies of the data gets corrupted, the data is lost (because you cannot tell which copy is the the good one).
In btrfs, being it checksummed, you can detect and fix the corrupted copy.
With a classic raid 1 you have double the chance of data corruption compared to a single device.
RAID1 is redundancy on device level. And that works also for mdadm or any other RAID1 implementation.
Redundancy on file level can only work if checksums are available. And that works well with ZFS also.
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Originally posted by EphemeralEft View Post
Unless what BTRFS calls “RAID1” is not really RAID1, that’s not correct; RAID1 only has as much usable capacity as the the size of its smallest member because every member in the RAID stores the same content.
btrfs RAID1 is this: It takes any number of disks with any size and it ensures that a data block has 2 copies residing on 2 different drives. Thats it. This is not what mdadm or ZFS call RAID1.
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