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dm-raid1 improvementsdm-raid1 improvementsPosted Apr 20, 2008 10:46 UTC (Sun) by nix (subscriber, #2304)In reply to: dm-raid1 improvements by wolfgang.oertl Parent article: Stable kernel 2.6.25 released Really? nix@loki 10 /home/nix% df -Pk / Filesystem 1024-blocks Used Available Capacity Mounted onOh, I can't be using md then: odd, I didn't know they had RAID-5 md-raid yet. Personalities : [raid1] [raid6] [raid5] [raid4]Hint: dm allows for a stack of block devices, and you can layer md both above it and (more usefully) below it. This particular system is using the fairly common configuration of LVM-atop-MD, thus is a dm-atop-md system. Checking whether you are using the device mapper is not the same thing as checking whether you are using dm-raid.
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dm-raid1 improvements Posted Apr 20, 2008 17:59 UTC (Sun) by sbergman27 (subscriber, #10767) [Link] Well, I am using the mapper. And if I dd from the /dev/mapper/VolGroupxx/LogVolxx/ to /dev/null and then do the same with /dev/sdax, which is the first member of the raid1 array, I get about 61MB/sec in both cases. So I guess I'm not getting read balancing in F8. Or, come to think of it, is the read balancing that fine-grained? I recall somebody telling me, a while back, that it only balanced reads from different processes, and not from the same process, or something like that.
dm-raid1 improvements Posted Apr 20, 2008 18:21 UTC (Sun) by nix (subscriber, #2304) [Link] I can't imagine dm could tell which process was originating the request, even if it wanted to. It's all one by that point.
dm-raid1 improvements Posted Apr 20, 2008 18:44 UTC (Sun) by sbergman27 (subscriber, #10767) [Link] Seemed odd to me, too. Another odd thing is that this kernel release, which I had not really thought was anything all that special, actually has not one, but at least two bombshell features. How did I miss the loud outcry which surely occurred when read balance support in raid1 was lost? And why have both its return, and the new TASK_KILLABLE functionality gotten so little notice?
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