Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi!
I ran onto very strange/odd problem. After reboot, after the _first_ mount
DRBD-device performance is only 30-35%, after unmounting and remounting -
it is just a bit slower that regular device (as expected). Tested it for
several times - results are the same... Basically:
[root at easy ~]# dd if=/dev/zero of=/var/test.file oflag=direct bs=1M count=5k
5120+0 records in
5120+0 records out
5368709120 bytes (5.4 GB) copied, 54.9302 s, 97.7 MB/s
[root at easy ~]# rm -f /var/test.file
[root at easy ~]# mount -o noatime,nodiratime /dev/drbd2 /u01
[root at easy ~]# dd if=/dev/zero of=/u01/test.file oflag=direct bs=1M count=5k
5120+0 records in
5120+0 records out
5368709120 bytes (5.4 GB) copied, 175.318 s, 30.6 MB/s
[root at easy ~]# rm -f /u01/test.file
[root at easy ~]# umount /u01
[root at easy ~]# mount -o noatime,nodiratime /dev/drbd2 /u01
[root at easy ~]# dd if=/dev/zero of=/u01/test.file oflag=direct bs=1M count=5k
5120+0 records in
5120+0 records out
5368709120 bytes (5.4 GB) copied, 55.4391 s, 96.8 MB/s
[root at easy ~]# rm -f /u01/test.file
[root at easy ~]# umount /u01
[root at easy ~]# mount /dev/drbd2 /u01
[root at easy ~]# dd if=/dev/zero of=/u01/test.file oflag=direct bs=1M count=5k
5120+0 records in
5120+0 records out
5368709120 bytes (5.4 GB) copied, 56.2754 s, 95.4 MB/s
I did several tests, results are the same.
Both /var and /u01 are on the same lvm group (which is built on top of
single PV). The only difference is that /var is mounted directly, and /u01
is mounted on top of DRBD device. Metadisk is a separate small LV in the
same VG.
OS is latest OracleLinux 6.5 (i.e. CentOS)
# modinfo drbd
filename: /lib/modules/3.8.13-26.2.1.el6uek.x86_64/updates/drbd.ko
alias: block-major-147-*
license: GPL
version: 8.4.4
description: drbd - Distributed Replicated Block Device v8.4.4
author: Philipp Reisner <phil at linbit.com>, Lars Ellenberg <
lars at linbit.com>
srcversion: 0F94090DFB0F3B579E526AE
depends: libcrc32c
vermagic: 3.8.13-26.2.1.el6uek.x86_64 SMP mod_unload modversions
disk {
on-io-error detach;
resync-rate 200M;
al-extents 16384;
disk-barrier no;
disk-flushes no;
}
But I tried different values (increased AL, disabled barriers/flushes) -
they do not chnge things.
Does anyone have any ideas? :-)
--
Best regards,
Alex
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