Hi Raja, On Sunday 22 Mar 2009, Raja Subramanian wrote: > On Sun, Mar 22, 2009 at 1:08 AM, Arun Khan <[email protected]> wrote: > > Has anyone done a 0+1 SW RAID? > > I had similar setups a few years ago when Linux did not have > native raid10 support. So I had to create two raid1 devices > and then stripe them with a raid0 device on top. > > My setup worked well enough for me to put into production use, > and I think they are still running. > > Instead of layering multiple raid levels, new Linux kernels offer > native raid10 support. I have not used this, it would be good > to research this further before making a decision. > > > I am thinking of configuring 2 disks (sda+sdc) in a RAID0 setup and > > then mirror this RAID device on the other 2 disks (sdb+sdd). > > Do not do it this way. If a single disk fails, the rebuild will take > too long. Better way to setup is like this: > > md0 = raid1 sda+sdc > md1 = raid1 sdb+sdd > md2 = raid0 md0+md1 > mkfs on md2 > > In case of sda failure, only sda+sdc need to be re-synced. > > Doing it your way will mean that md0 and md1 need to be > re-synced and will take double the time. > > > Note that as long as you are not doing RAID parity computation, > as in RAID5/6, SW raid has absolutely no CPU hit. SW RAID0/1 > are all good in my book.
Thanks much for sharing your experience on nested raid. I found the following discussion also very useful. <http://en.wikipedia.org/wiki/Nested_RAID_levels> There is no doubt, it needs to be planned out and then implemented. The main motivation for considering RAID, I want to implement VMs with the virtual disks on RAID to take advantage of striping. I am wondering if is there any significant advantage of doing sw RAID 1+0 (4 disks) v/s sw RAID5 (3 disks). Thanks again. -- Arun Khan _______________________________________________ To unsubscribe, email [email protected] with "unsubscribe <password> <address>" in the subject or body of the message. http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
