On Fri, Jul 18, 2008 at 01:28:26PM +0200, Goswin von Brederlow wrote: > martin f krafft <madduck@debian.org> writes: > > > also sprach Ryan Niebur <ryanryan52@gmail.com> [2008.07.17.2137 +0200]: > >> Here is a patch that adds support for RAID6 and RAID10 to the > >> debian installer. > > > > Wow! Thanks! > > > >> +_Description: Number of active devices for the RAID6 array: > >> + The RAID6 array will consist of both active and spare partitions. The active > >> + partitions are those used, while the spare devices will only be used if one or > >> + more of the active devices fail. A minimum of three active devices is > >> + required. > > > > I think it's four, isn't it? > > 3 is theoretical possible although it makes no sense. A raid1 with 2 > mirrors would be better there. > Since the existing code for RAID5 requires 3 drives, I'm going to have the RAID6 code require 4 drives. > >> + NOTE: this setting cannot be changed later. > > > > It can, but not trivially. > > > >> +Template: mdcfg/raid10devcount > >> +Type: string > >> +# :sl3: > >> +_Description: Number of active devices for the RAID10 array: > >> + The RAID10 array will consist of both active and spare partitions. The active > >> + partitions are those used, while the spare devices will only be used if one or > >> + more of the active devices fail. A minimum of four active devices is > >> + required. > > > > You can have RAID10 across two devices, although it makes no sense, > > really. > > Raid10 allows different layouts. For a single stream access a 2 disk > raid 10 with far copies reads twice as fast as raid1. Raid 1 only uses > both disks when you have 2 streams reading. > > Further raid10 over 3 devices with 2 copies makes sense too. It gives > you 1.5* the space and can handle one disk failing without the cpu > cost of raid5. > In my next patch it is changed to a minimum of 2 for RAID10. > > I haven't had time to look at your patch in depth, but it's looking > > good. Unfortunately it's probably too late for lenny... > > I haven't looked at the path either but I hope the raid10 asks for the > number of copies and layout to be used. Those are important factors. > If not then that would be an important feature that is missing. > Yes, it does. > MfG > Goswin -- _________________________ Ryan Niebur RyanRyan52@gmail.com
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