I'm not sure if the kernel raid10 module is the same as building a RAID0 md device out of multiple RAID1 devices. We used to use the later to create a RAID10 device by striping Linux SW RAID1 devices. We had great luck creating a RAID10 array out of a large number of disk spindles. So in your /etc/raidtab (or /etc/mdadm.conf) your RAID0 /dev/md2 would consist of striping across /dev/md0 and /dev/md1. In your diagram below your HDD1 and HDD2 would be mirrored to create either md0 or md1 and HDD3 and HDD4 would then be the other md device. I know how that works and it worked reliably for me so that's what I would recommend doing. BTW, you could only survive a 2 disk failure if they were the "correct" 2 disks. If both HDD1 and HDD2 would fail then you would be out of luck. Again, I've never used the kernel raid10 module, and I haven't been able to find any good (visual) information on the module to be able to determine how the module would survive disk failures. I would assume it's the same as the striping of RAID1 devices that I described above, but I don't like to assume ;) Good luck, Andy. -----Original Message----- From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of Tomasz Chmielewski Sent: Thursday, August 10, 2006 4:48 AM To: linux-raid@xxxxxxxxxxxxxxx Subject: RAID-10 and 4 HDDs - how many HDDs can break without loosing data? I want to set up RAID-10 on 4 400 GB drives, on not-so powerful machine (600 MHz ARM, Thecus n4100) - to have a total of 800 GB storage, with some protection against a drive failure. As the machine is not very powerful, I don't want to use RAID-5 nor RAID-6. Previously, I would use RAID-0 on top of two RAID-1s: ----RAID0---- | | RAID1 RAID1 | | | | HDD1 HDD2 HDD3 HDD4 With RAID-0 on top of RAID-1, with 4 drives, I would achieve: - 100% chance of recovery if any single, one disk fails, - 50% chance of recovery if any two disk failure. Now with RAID-10 in the Linux kernel, what are my chances of recovering from a single and two disk failure? RAID10 ------------------ | | | | HDD1 HDD2 HDD3 HDD4 Is it also 100% if one disk fails, and 50% if two disks fail? Or perhaps, with 4 drives, RAID-10 can survive any 2 disks failure? -- Tomasz Chmielewski http://wpkg.org - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html Confidentiality Notice: This e-mail message including attachments, if any, is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. If you are the intended recipient, but do not wish to receive communications through this medium, please so advise the sender immediately. - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
