12/5 In RAID 1, when I write, is it a synchronous write to both drives?
In another word, is my write complete upon verifying BOTH drives
have written (indicating the slowest drive = bottleneck)? How about
read? Does RAID 1 require reading both drives, comparing results,
then returning them? Or can it do striping read?
\_ Write completes when it has written to both so RAID1 writes are
usually a little slower than writing to a single disk. Reads are
from one only, which is why RAID1 has very good read performance.
You can read different data off of both drives at the same time.
Remember, RAID1 doesn't stripe at all. Your drives should be
identical to avoid one being much slower than the other.
\_ What if the first read gives me bogus data (or data that
is different than the second data because a neutrino particle
changed a few bits)?
\_ You don't use RAID1 to protect against that. If the two
bits were different how would the system know which was
correct? There's no parity information with RAID1.
\- hello, YMWTGF(zfs, merkle tree). btw, if you see this happen
i'd recommend focusing on the neutrino changing some bits
and forget about the integrity of the data. --psb
\_ We should start up that Silicon Valley CSUA blacklist again, since
CSUA has a hammerlock on the economy. |
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