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Re: [lvm-devel] LVM2 test script failed, is it a read_ahead bug?



Dne 27.8.2013 12:00, Dongmao Zhang napsal(a):
Dear mail-list,
     I met this in running the test case for lvm:
sh shell/read-ahead.sh FAILED:



-               if (current_read_ahead >= read_ahead) {
+               if (current_read_ahead <= read_ahead) {
                         log_debug_activation("%s: retaining kernel read
ahead of %" PRIu32
                                   " (requested %" PRIu32 ")",
                                   dev_name, current_read_ahead, read_ahead);

If I am wrong, please correct me:)



Basic rules for 'auto'mated read_ahead setting is simple: never set smaller value then the one which has been already set by kernel when device has been initialized.

If you need any specific more 'clever' value - simply use direct value for
lvcreate/lvchange --readahead.

There is no thing like 'minimal' RA estimation in lvm2.

It's quite tricky to estimate the ideal RA for devices and it mostly depends
on the type of use.

Zdenek


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