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Raid 1, being a mirror, depends on all disks in a mirror being exact copies of each other. Take your random hard drive, and another random hard drive, and you possibly have different data there, thus violating this presumption. This is why initialization is needed. It simply copies contents of the first drive to others. Note that in some conditions you can ...


Initial synchronization is needed because any differences between the mirrors would show up as errors during the periodic check. And you should be doing periodic checks.


Simply put because two new disks are not expected to be mirror perfect copies of each other from the onset. They need to be turned into perfect copies of each other. In addition initialization includes setting up the metadata superblock with information about the array configuration as well. The /proc/mdstat file should tell you that the device has ...


Remember that RAID 1 is a mirror, and that RAID 10 is a stripe of mirrors. The question is, on which disk in each mirror is the data valid? In a freshly created array, this cannot be known, as the disks may have different data. Remember also that RAID operates at a very low level; it knows nothing of filesystems or whatever data might be stored on the ...


RAID 1 is 1/2 as fast write as a regular disk Raid 0 is 2x as fast write as a regular disk. (1/2) * 2 = 1 if you have 4 disks in Raid 10 you will get 1x the write speed and 4x the read speed. These are general numbers and not technical numbers as random/sequential and other factors come into play (Although not so much with SSD).


I could close this as a duplicate because there are a lot of factors that impact storage performance in Linux. I think people have the wrong idea when they attempt to benchmark SSD performance. You should use SSDs for better random I/O performance. You're testing big-block sequential performance, which doesn't match any sort of use case except for, um, ...

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