Thanks a lot for you, and Raz! The raw devices readahead I already set with the hdparm, and /sys/block/*/queue/read_ahead_kb, but the md device is only changeable with blockdev. :-) I dont use lvm, because it is too slow for me.... But unfortunately the problem is still here for me. :( I continue searching the bottleneck... Thanks! Janos ----- Original Message ----- From: "David Greaves" <david@xxxxxxxxxxxx> To: "Raz Ben Jehuda" <razb@xxxxxxxxxxx> Cc: <djani22@xxxxxxxxxxxxx>; <linux-raid@xxxxxxxxxxxxxxx> Sent: Thursday, August 04, 2005 4:56 PM Subject: Re: RAID5 question. > And notice you can apply different readahead to: > The raw devices (/dev/sda) > The md device (/dev/mdX) > Any lvm device (/dev/lvm_name/lvm_device) > > David > > Raz Ben Jehuda wrote: > > >read the blockdev man page > > > >On Thu, 2005-08-04 at 16:06 +0200, djani22@xxxxxxxxxxxxx wrote: > > > > > >>Hi list, Neil! > >> > >>I have a little question because I'v got some performance problem... > >>Is the RAID5 do any type of headahead with the default config? > >>It is possible to disable the readahead? (if it is.) > >>Or just the io_sched do that on the disks? > >> > >>How can I disable the whole headahead on top of the RAID5 array? > >> > >>The RAID5 can do multiple small (<4kb) reads of disks for the multithreaded > >>read requests? > >>(chunk size is 32k) > >> > >>Thanks for helping! > >> > >>Janos > >> > >>- > >>To unsubscribe from this list: send the line "unsubscribe linux-raid" in > >>the body of a message to majordomo@xxxxxxxxxxxxxxx > >>More majordomo info at http://vger.kernel.org/majordomo-info.html > >> > >> > > > -- > > - > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
