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Date: Tue, 10 Jun 2008 17:13:31 +0200 (CEST)
From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
To: Erik Trulsson <ertr1013@student.uu.se>
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Cc: freebsd-questions@freebsd.org, DA Forsyth <iwrtech@iwr.ru.ac.za>
Subject: Re: xRAID disks....
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x> hardware support.
>
>> actually there is not much need to have it for RAID-0/1/10 where there is
>> almostnothing to process.
>
> For mirrors it can actually be a big win with hardware support.
> If you use software RAID then you will have to perform each write twice
> (once to each disk),
in parallel
> while with hardware support for RAID you only need
> to transfer the data once.

which saves at most 100MB/s bandwidth - compare this to 5-10GB/s in modern 
machines.

If the controller resides on a PCI-bus together
> with several other devices (which is not uncommon) then the reduced
> bandwidth usage can be very useful.

true. but not if it's builtin in chipset or on PCI express.


there are really not worth price. unless you need RAID-5.

but with todays disk prices it's better to just use RAID-1+0 and bigger 
drives.

with software RAID you are not forced to operate on whole disks. usually 
not everything has to be mirrored.