Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Dear list, When looking into performance tuning DRBD, I found the max-bio-bvecs settings as a performance factor. I set it to 1 due to the comment below (which is slow). Is this problem still the case (we are using DRBD version 8.4.0-1)? Can one enforce the alignment settings for ext3/ext4? # In some special circumstances the device mapper stack manages to # pass BIOs to DRBD that violate the constraints that are set forth # by DRBD's merge_bvec() function and which have more than one bvec. # A known example is: # phys-disk -> DRBD -> LVM -> Xen -> missaligned partition (63) -> DomU FS # Then you might see "bio would need to, but cannot, be split:" in # the Dom0's kernel log. # The best workaround is to proper align the partition within # the VM (E.g. start it at sector 1024). (Costs 480 KiByte of storage) # Unfortunately the default of most Linux partitioning tools is # to start the first partition at an odd number (63). Therefore # most distribution's install helpers for virtual linux machines will # end up with missaligned partitions. # The second best workaround is to limit DRBD's max bvecs per BIO # (= max-bio-bvecs) to 1. (Costs performance). # max-bio-bvecs 1; Thanks in advance, Jakob