On Mon, 8 Oct 2007, Janek Kozicki wrote:
Hello, Recently I started to use mdadm and I'm very impressed by its capabilities. I have raid0 (250+250 GB) on my workstation. And I want to have raid5 (4*500 = 1500 GB) on my backup machine. The backup machine currently doesn't have raid, just a single 500 GB drive. I plan to buy more HDDs to have a bigger space for my backups but since I cannot afford all HDDs at once I face a problem of "expanding" an array. I'm able to add one 500 GB drive every few months until I have all 4 drives. But I cannot make a backup of a backup... so reformatting/copying all data each time when I add new disc to the array is not possible for me. Is it possible anyhow to create a "very degraded" raid array - a one that consists of 4 drives, but has only TWO ? This would involve some very tricky *hole* management on the block device... A one that places holes in stripes on the block device, until more discs are added to fill the holes. When the holes are filled, the block device grows bigger, and with lvm I just increase the filesystem size. This is perhaps coupled with some "unstripping" that moves/reorganizes blocks around to fill/defragment the holes. is it just a pipe dream? best regards PS: yes it's simple to make a degraded array of 3 drives, but I cannot afford two discs at once... -- Janek Kozicki | - 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
With raid1 you can create a degraded array with 1 disk- I have done this, I have always wondered if mdadm will let you make a degraded raid 5 array with 2 disks (you'd specify 3 and only give 2) - you can always expand later.
Justin. - 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
