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Re: Questions about RAID 6

On Mon, May 3, 2010 at 6:02 AM, Boyd Stephen Smith Jr.
<bss@iguanasuicide.net> wrote:
> On Sunday 02 May 2010 06:00:38 Stan Hoeppner wrote:
> Speeds on my md-RAID devices were comparable to speeds with my Areca HW RAID
> controller (16-port, PCI-X/SATA, battery powered 128MB cache).  Number of
> drives varied from 5 to 10.  RAID levels 5 and 6 were both tested.
> Read throughput for both were the expected (# drives - # parity drives) *
> single drive throughput.  Write throughput less than expected in both cases,
> but I can't recall the exact figures.
> It might be different when the system is under load, since the md-RAID depends
> on the host CPU and the HW RAID does not.  However, adding an additional
> generic CPU (to reduce load) is both more useful and often less expensive than
> buying a HW RAID controller that is only used for RAID operations.

My system used to become close to unusable on the 1st sunday of the month when
mdadm did it resync, I had to write my own script so it did not do
mulitple at the
same time, turn off the hung process timer and set cpufreq to performance.

Now with hd ware raid I don't notice it


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