On Tue, Feb 14, 2017 at 11:48:51AM -0800, Shaohua Li wrote: > On Mon, Feb 13, 2017 at 05:07:45PM +0800, Chien Lee wrote: > > Hello, > > > > > > Recently we find a bug about skip_copy feature in raid5 degraded mode. > > In the beginning, we enable the skip_copy feature to speed up system’s > > write performance. But when the system has database read/write I/O > > continually in raid5 degraded mode, the Mongo DB will detect the > > checksum error and generate related debug log. The following is the > > testing detail. > > > > > > a. Enable skip_copy > > --> Checksum error logs from Mongo DB > > > > 2017-02-06T11:54:56.537+0800 E STORAGE [conn7] WiredTiger (0) > > [1486353296:537114][52:0x7f98396a4700], > > file:collection-110-3235234017846331078.wt, WT_CURSOR.next: read > > checksum error for 4096B block at offset 61440: calculated block > > checksum of 1363526237 doesn't match expected checksum of 2969711960 > > > > > > b. Disable skip_copy > > --> Mongo DB has no checksum error. > > > > > > We've pretty sure that it must be a bug by our repeated database I/O > > testing. When skip_copy feature is enabled, the raid5/raid6 always > > causes the mongo DB checksum error in degraded mode less than one > > hour. On the contrary, it will never cause this abnormal situation > > when the skip_copy feature is disabled. Besides, because the skip_copy > > feature only affects the write action instead of read action, I think > > it should be the write action in degraded mode while skip_copy feature > > is enabled cause this bug. > > > > > > Please kindly provide us some help or idea about the root cause and solution. > > Thanks for the reporting, I'll look at it. In the meaning time, do you have a > quick way which I can use to reproduce the issue? Can't find anything suspicious after checking a while. Can you describe the setup/test in detail? like if there is sync running, IO error? -- 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
