Mikael Abrahamsson wrote:
On Fri, 14 Nov 2008, Billy Crook wrote:
Obviously RAID-class drives benefit in hardware raid (with hardware
raid controllers). But do RAID-class drives benefit when used on a
non-raid hardware controller, with linux software raid (mdadm)? What
about a hardware raid controller in JBOD mode?
This is not a HW vs SW issue, it has to to with the behaviour of the
drives in conjunction with the OS when a certain thing happens.
In a non-raid environment, you want to read the data at any cost, so
waiting 2 seconds for it to read is no real problem, you just want the
data.
In a raid environment you can reproduce the block by way of mirror or
parity, so you want the read to fail after a short time so it won't delay
the reading of the data.
Here is a paper about the Western Digital feature "TLER", which is used
in all their RE series RAID drives.
http://www.wdc.com/en/library/sata/2579-001098.pdf
In addition, these drives are better able to cope with the problem of
mechanical vibration/resonance that occurs when multiple drives are
mounted in close proximity:
http://www.wdc.com/en/library/sata/2579-001079.pdf
These features will benefit HW and SW RAID implementations.
I have no association with Western Digital, other than as a satisfied user.
Regards,
Richard
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