The answer is more difficult! I use RAID-s in 3 layers! Layer 1 : (RAID5 in 11+1 raw disk in 1 pc) x4 (4 disk nodes) Layer 2 : RAID1 4x 1/2 nodes (only for ability to backup complete nodes) Layer 3 : RAID0 to 4 nodes -> 1 big 8TB disk. :-) I use gnbd for this. The gnbd sends only small packets, and I think, the too much readahead is the problem, because the whole 8TB array is phisically stripped to 44 raw disks, but NOT! When I disable the readahead, the performace is more worse. Now I grow the readahead in the raw disk to 1MB, the raid5 to 10MB, the raid1 to 1MB, and the raid0 to 8MB, and the performance is great now! :-) (web+ftp server for ~200-300 people at one time, downloading a lot of small(1-60KB) and big (~15-50MB) files) Thansk for you all! ----- Original Message ----- From: "Raz Ben Jehuda" <razb@xxxxxxxxxxx> To: <djani22@xxxxxxxxxxxxx> Cc: <linux-raid@xxxxxxxxxxxxxxx> Sent: Thursday, August 04, 2005 6:25 PM Subject: Re: RAID5 question. > how is the disks performance ? is it OK ? > > On Thu, 2005-08-04 at 18:13 +0200, djani22@xxxxxxxxxxxxx wrote: > > Yes, it is there, I know it. > > But its only for resync or not? :-) > > > > ----- Original Message ----- > > From: "Raz Ben Jehuda" <razb@xxxxxxxxxxx> > > To: <djani22@xxxxxxxxxxxxx> > > Cc: "David Greaves" <david@xxxxxxxxxxxx>; <linux-raid@xxxxxxxxxxxxxxx> > > Sent: Thursday, August 04, 2005 5:56 PM > > Subject: Re: RAID5 question. > > > > > > > take a look at /proc/sys/dev/raid/speed_limit_max . it is kilobytes if i > > > recall correctly. > > > > > > On Thu, 2005-08-04 at 17:45 +0200, djani22@xxxxxxxxxxxxx wrote: > > > > 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 > > > -- > > > Raz > > > Long live the penguin > > > > > > - > > > 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 > > > -- > Raz > Long live the penguin > > - > 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
