Hi I know it''s not in yet, but is there a plan to implement raid-z(2)- like operation? I have heard of plans to integrate with the existing md-subsystem in the kernel, but I''m not sure if this will be appropriate comparing this to how things are done in zfs/raid-z. roy -- Roy Sigurd Karlsbakk (+47) 97542685 roy@karlsbakk.net http://blogg.karlsbakk.net/ -- I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med fremmed opprinnelse. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 2009-07-10 at 10:58 +0200, Roy Sigurd Karlsbakk wrote:> I know it''s not in yet, but is there a plan to implement raid-z(2)- > like operation? I have heard of plans to integrate with the existing > md-subsystem in the kernel, but I''m not sure if this will be > appropriate comparing this to how things are done in zfs/raid-z.I''m currently working on the basic implementation of RAID5/RAID6 (qv). I don''t think there''ll be much integration with the md subsystem -- we''ll probably just shift the cunning GF arithmetic out into lib/raid6 or something, then let them both use it from there. We do want to do full stripe writes to the RAID[56] parts, so we''re going to want to do something like falling back to RAID1 (or to a RAID5 chunk with smaller stripe length) for smaller allocations. That''s basically what you''re talking about, isn''t it? -- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 11. juli. 2009, at 16.59, David Woodhouse wrote:> On Fri, 2009-07-10 at 10:58 +0200, Roy Sigurd Karlsbakk wrote: >> I know it''s not in yet, but is there a plan to implement raid-z(2)- >> like operation? I have heard of plans to integrate with the existing >> md-subsystem in the kernel, but I''m not sure if this will be >> appropriate comparing this to how things are done in zfs/raid-z. > > I''m currently working on the basic implementation of RAID5/RAID6 (qv). > I don''t think there''ll be much integration with the md subsystem -- > we''ll probably just shift the cunning GF arithmetic out into lib/raid6 > or something, then let them both use it from there. > > We do want to do full stripe writes to the RAID[56] parts, so we''re > going to want to do something like falling back to RAID1 (or to a > RAID5 > chunk with smaller stripe length) for smaller allocations. That''s > basically what you''re talking about, isn''t it?In ZFS/RAIDZ(2) they are said to use RAID3-like partial writes as with with a file-level redundancy, meaning if a file won''t cover a whole stripe, it''ll use a partial one. I''m not sure if this is the case, but it''s what I''ve been told by the people from Sun. This may open for fewer IOPs per write. Is something like this in the thoughts of the new RAID[56] in BTRFS? roy -- Roy Sigurd Karlsbakk (+47) 97542685 roy@karlsbakk.net http://blogg.karlsbakk.net/ -- I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med fremmed opprinnelse. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html