[CentOS] question about software Raid 1
John R Pierce
pierce at hogranch.com
Sun Sep 21 18:12:17 UTC 2008
> Does software raid 1 compare checksums or otherwise verify that the same
> bits are coming from both disks during reads? What I'm interested in,
> is whether bit errors that were somehow undetected by the hardware would
> be detected by the raid 1 software.
under normal operation, each read request goes to one or the other
drive, this doubles the read throughput as both drives can be servicing
different read requests at the same time.
some raid does a scrub, where in the background, when the disks are
otherwise idle, it gradually reads all the raid stripes and validates
them. I honestly don't know if Linux built in raid does this or
not. Of course, with RAID-1, if the two blocks disagree, there's no
way of knowing which one is correct, only that there is a potential problem.
Some raid (Sun ZFS, for instance) stores a checksum with every block so
it can detect corruption immediately. Also, I know ZFS does this
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