At 21:35 03/03/2014, you wrote: ´¯¯¯
RAID3-4-5 was great when disks were expensive, in 80's an 90's. Now not. A minimal RAID5 needs 3 disks. A minimal RAID10 4. An enterprise disk SAS 15Krpm 146 GB 6G is $350, and a not enterprise grade cheaper and bigger. Now RAID1E and RAID10E give more flexibility and variable security, from "paranoid" to "i don't care" grades.
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The point being discussed was not on performance or cost, but on the imaginary fact that RAID5-6 and variations have the inherent, by-design fatal flaw that they break down because a parity block can be out of sync with corresponding data blocks. This is bullshit, period.
Nothing in RAID5-6 design mandates serialization of writes, by far. It's only when cheap, unreliable hardware is put to work under below par software that the issue can be a real-world problem.
So the rant on the design against parity-enabled RAIDs is moot, if not plain fallacious unless "software RAID without dedicated controller" is clearly mentionned.
About SAS disks: they have actual very high reliability and don't lie, contrary to SATA disks (on both points).
This is not a war about mine being bigger, but it's better to have facts stated right. All high-end reliable machines and storage subsystems only run parity-enabled RAID levels and this thechnology isn't going to disappear tomorrow.
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