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> Cc: freebsd-questions@freebsd.org, DA Forsyth <iwrtech@iwr.ru.ac.za> Subject: Re: xRAID disks.... Message-ID: <20080610171129.K75322@wojtek.tensor.gdynia.pl> In-Reply-To: <20080610150536.GA67056@owl.midgard.homeip.net> References: <484EACEB.7169.43FE1258@iwrtech.iwr.ru.ac.za> <20080610165435.M68290@wojtek.tensor.gdynia.pl> <20080610150536.GA67056@owl.midgard.homeip.net>
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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.
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