Thanks for all of the inputs...I finally came across a good article summarizing what I needed, looks like I am going to try to the f2 option and then do some testing vs the default n2 option. I am building the array as we speak but it looks like building the f2 option will take 24hrs vs 2hrs for the n2 option....this is on 2 1TB hdd.... On Sat, Sep 25, 2010 at 3:04 PM, Ross Walker <rswwalker at gmail.com> wrote: > On Sep 25, 2010, at 1:52 PM, Tom H <tomh0665 at gmail.com> wrote: > > > On Sat, Sep 25, 2010 at 11:48 AM, Ross Walker <rswwalker at gmail.com> > wrote: > >> On Sep 25, 2010, at 9:11 AM, Christopher Chan < > christopher.chan at bradbury.edu.hk> wrote: > >>> Jacob Bresciani wrote: > >>>> RAID10 requires at least 4 drives does it not? > >>>> > >>>> Since it's a strip set of mirrored disks, the smallest configuration I > >>>> can see is 4 disks, 2 mirrored pairs stripped. > >>> > >>> He might be referring to what he can get from the mdraid10 (i know, > Neil > >>> Brown could have chosen a better name) which is not quite the same as > >>> nested 1+0. Doing it the nested way, you need at least 4 drives. Using > >>> mdraid10 is another story. Thanks Neil for muddying the waters! > > > > > >> True, but if you figure it out mdraid10 with 2 drives = raid1, you would > need 3 > >> drives to get the distributed copy feature of Neil's mdraid10. > > > > I had posted earlier ( > > http://lists.centos.org/pipermail/centos/2010-September/099473.html ) > > that mdraid10 with two drives is basically raid1 but that it has some > > mirroring options. In the "far layout" mirroring option (where, > > according to WP, "all the drives are divided into f sections and all > > the chunks are repeated in each section but offset by one device") > > reads are faster than mdraid1 or vanilla mdraid10 on two drives. > > If you have any two copies of the same chunk on the same drive then > redundancy is completely lost. > > Therefore without loosing redundancy mdraid10 over two drives will have to > be identical to raid1. > > Reads on a raid1 can be serviced by either side of the mirror, I believe > the policy is hard coded to round robin. I don't know if it is smart enough > to distinguish sequential pattern from random and only service sequential > reads from one side or not. > > >> For true RAID10 support in Linux you create multiple mdraid1 physical > >> volumes, create a LVM volume group out of them and create logical > >> volumes that interleave between these physical volumes. > > > > Vanilla mdraid10 with four drives is "true raid10". > > Well like you stated above that depends on the near or far layout pattern, > you can get the same performance as a raid10 or better in certain workloads, > but it really isn't a true raid10 in the sense that it isn't a stripe set of > raid1s, but a distributed mirror set. > > Now don't get me wrong I'm not saying it's not as good as a true raid10, in > fact I believe it to be better as it provides way more flexibility and is a > lot simpler of an implementation, but not really a raid10, but something > completely new. > > -Ross > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.centos.org/pipermail/centos/attachments/20100925/10a57538/attachment-0005.html>