Woha. Lot's of replies :) 1) Speed is generally not the biggest importance. 5-6MB/s would be enough. All drives are UDMA 100, and there are 4 UDMA 100 host controllers in this system. If I want to, I can have 16 drives. The speed varyes between 25-35MB/s for all drives. The reason I choose a RAID 5 setup was that one drive could die (to the point where no data recovery is possible) without loosing any data. If the system gets very slow, or I might even have to bring it down to replace the drive, that's fine. I only need enough security if one drive would fail. Agreed, mirroring would perhaps be safer, and at least faster when a drive failes. But I need as much diskspace I can get, and mirroring would consume alot of that. Thanks, Anders > On Wed, 10 Apr 2002 08:01, you wrote: > but that REQUIRES, that the disks are not >> hd<a,b,c,d,e,f,g,h> >> You should try to avoid having more than one (active) disk at the same >> controller at once. > I've always wondered about this statement. > The idea AFAIK is that unlike SCSI, IDE has the master drive control the > slave drive on the same controller. > 1) This causes problems where the drives are a different > model/make/manufactuer as the master drive will downgrade the settings of the > drives (master & slave) to the lowest common denominator; and therefore, the > speed in this case is affected. > 2) Having the master drive control the slave drive also causes problems if > the master fails as then both drives fail or if a drive takes down the chain > both drives fail. > 3) maybe a couple of others that I have forgotten at the moment. > When I was setting up my server at home 1.2GAthlon AsusA7V-133 384M RAM 9x > IBM 40G drives, 1 Promise Ultra100 & 2 Promise Ultra100TX2 I did a couple of > tests. > I found by using a flaky drive from a previous life (a western digital that > when it would die would take down the controller) that it didn't matter if > the drive was a single master on a controller, a master on a shared > controller or a slave on a shared controller. When the drive would fail - it > would take the whole machine down with it. The Kernel would not die but it > would deadlock waiting for interrupts to return and the only way to fix the > issue was to hard reset. Having the flaky dirve as a standalone drive or as > part of a software RAID made no difference. So I concluded that at least in > my setup I gained nothing by only having one IDE drive per controller. > I also ran bonnie++ tests on a software RAID0 using 4 master only drives > (hde, hdg, hdi, hdk) and 4 master-slave drives (hde, hdf, hdg, hdh). The > results of the test were that seek times for the master-slave case were half > that for the master-master case. Read times did drop but only by about > .75M/s from 80M/s but the write times improved by about .25-.75M/s from > 50M/s. So I concluded that at least for my setup it was better to have the > master-slave case because the loss of read speed was made up by the increase > in write speed. > So my final configuration was that hda, hdb were system disks. The RAID5 > used hde, hdg, hdi, hdk with a hot spare hdo and the RAID0 used hdm & hdn. > Now the tests weren't what I would call conclusive or proper scientific tests > but I believe they were valid. I've always wondered what others have found > as what I found seems to fly in the face of common rules of thumb. > There is a specific mailing list "linux ide" > <linux-ide-arrays@lists.math.uh.edu> that deal with large IDE arrays so you > might like to also ask your question there and see what is suggested. _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html
