[DRBD-user] kernel: drbd0: bio would need to, but cannot, be split

hans morbus2000 morbus2000 at web.de
Thu Aug 13 18:07:30 CEST 2009

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


we add the following parameter in drbd.conf

disk {
    	max-bio-bvecs 1;

and ...

# echo 4 > /sys/block/sdb/queue/max_sectors_kb

now, the performance of the 3ware 9550 is very slow

# hdparm -tT /dev/sda
Timing cached reads:   8472 MB in  2.00 seconds = 4246.06 MB/sec
Timing buffered disk reads:  130 MB in  3.04 seconds =  42.81 MB/sec

I've applied the standard 3ware tuning values
echo 128 > /sys/block/sda/queue/max_sectors_kb (default 128)
/sbin/blockdev --setra 16384 /dev/sda

and the performance goes to

# hdparm -tT /dev/sda
Timing cached reads:   8152 MB in  2.00 seconds = 4083.90 MB/sec
Timing buffered disk reads:  828 MB in  3.01 seconds = 275.36 MB/sec

can we change backwards max_sectors_kb to 128
without to get the same error?

Best Regards

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