Thanks Peter, Your description of my question was spot on :) thanks. Luckily we dont have those discs set up yet... I shall enquire further on linux-raid as to what experimental might actually mean in this context.
regards mark On Mon, Nov 28, 2011 at 3:07 PM, Peter M. Petrakis < [email protected]> wrote: > > > On 11/26/2011 04:35 AM, Mark van Harmelen wrote: > > Hi > > > > Thanks to those who contributed to a discussion on software raid > > recently, it changed my mind about the universal desirability of > > hardware raid cards. > > > > So now I'm intent on building a sw raid based machine, but mostly am > > interested in performance under disc load. > > > > Basic question: given a number of spare cores (be they hyperthreaded > > or not) is ubuntu's sofware raid clever enough to be able to deal > > with multiple read and write requests simultaneously, one request per > > spare core? Or would I expect only to see one of the spare core > > utilised? > > Request level might be the the wrong level to look at, Linux already has > lots of queue level optimizations. What's really going to matter here is > efficiently handling parity calculations and the effective RAID > real estate (stripes). There does appear to be a multi-core optimization > for MD RAID5/6 and it's disabled by default on Ubuntu kernels. > > http://lxr.linux.no/linux+v3.1.3/drivers/md/Kconfig#L157 > > config MULTICORE_RAID456 > bool "RAID-4/RAID-5/RAID-6 Multicore processing (EXPERIMENTAL)" > depends on MD_RAID456 > depends on SMP > depends on EXPERIMENTAL > ---help--- > Enable the raid456 module to dispatch per-stripe raid operations > to a > thread pool. > > If unsure, say N. > > $ grep MULTICORE_RAID456 /boot/config-3.0.0-1* > /boot/config-3.0.0-12-generic:# CONFIG_MULTICORE_RAID456 is not set > /boot/config-3.0.0-13-generic:# CONFIG_MULTICORE_RAID456 is not set > > It looks like a work in progress, I hope you have nothing to lose on those > disks. > See the linux-raid list for more information: > http://marc.info/?l=linux-raid . > > Peter > > > > > thanks mark > > > > > > -- > ubuntu-server mailing list > [email protected] > https://lists.ubuntu.com/mailman/listinfo/ubuntu-server > More info: https://wiki.ubuntu.com/ServerTeam >
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