[CentOS] RE: IDE RAID support -- FRAID v. intelligent hardware RAID
Bryan J. Smith
b.j.smith at ieee.orgFri Jul 22 12:19:07 UTC 2005
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Nick Bryant <nick at everywhereinternet.com> wrote: > Indeed. I freaked out when I couldn't get my sata promise > raid controlling working in Acer Altos series servers... > Till I read an article that said in 2.4 its actually just > as quick (if not quicker, depending on server hardware) > to let the kernel deal with the raid stuff. The Logical Disk/Volume Management (LDM/LVM) of the OS is always going to order, schedule and commit far more efficiently than a FRAID driver (FRAID cards have *0* intelligence, only a "trick" 16-bit BIOS that is _useless_ once the OS boots). Software RAID-0 may be faster than hardware (especially if spread over cards on separate PCI channels). Software RAID-1 and 10 require the I/O commit 2x the data over hardware RAID, which just takes the 1:1 stream. Software RAID-3/4/5 push _all_ data through the CPU-memory- I/O interconnect, and is detrimental on the limited CPU- memory-I/O interconnect (the XORs aren't the problem), whereas hardware RAID-3/4/5 just takes the 1:1 stream. -- Bryan J. Smith mailto:b.j.smith at ieee.org Sent from Yahoo Mail (please excuse any missing headers)
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