2012-10-27 20:54, Toby Thain wrote:
Parity is very simple to calculate and doesn't use a lot of CPU - just
slightly more work than reading all the blocks: read all the stripe
blocks on all the drives involved in a stripe, then do a simple XOR
operation across all the data. The actual checksums are more expensive
as they're MD5 - much nicer when these can be hardware accelerated.
Checksums are MD5??
No, they are fletcher variants or sha256, with more probably coming
up soon, and some of these might also be boosted by certain hardware
capabilities, but I tend to agree that parity calculations likely
are faster (even if not all parities are simple XORs - that would
be silly for double- or triple-parity sets which may use different
algos just to be sure).
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