Hello,
I have a backup time degradation problem.
In a nutshell (it looks a write latency performance):
- the old IO pair ( SLES10 + drbd 8.2.6 ) can finish the task in 10 seconds
- the new IO pair ( SLES11SP2 + drbd 8.3.12 ) can do it in 16 seconds only.
I can force the old 8.2.6 configuration to slow down if I comment
out
no-disk-flushes ;
no-md-flushes ;
from the disk section in the config file.
When I change the 8.3.12 configuration, it has no effect on speed.
I can prove this "slow down" with the 'standard' drbd latency measurement
command:
dd if=/dev/zero of=/opt/mirror/perftest/sles.latency-bs512-count4096 bs=512
count=4096 oflag=direct
In this special case the new system is 4 times slower!
Questions:
A) - Is it a known issue for the 8.3.12 drbd ? ( no-disk-flushes no-md-flushes
has no real effect )
B) - I have checked the sysctl and io-scheduler settings and tried to
tune the SLES IO performance with no success.
// I used :
http://www.suse.com/documentation/sles11/pdfdoc/book_sle_tuning/book_sle_tuning.pdf
// and alsohttp://www.drbd.org/users-guide/s-throughput-tuning.html
Is there any hint to try?
I must admit that the throughput test shows 20% advantage,
but I do not mind if it becomes worse, if I can tune up the latency.
Thanks your help in advanced:
BR,
Akos
Here is my config if anyone need it
-----------------------------------------------
drbd IO configuration on a SLES10 installation:
-----------------------------------------------
# drbdsetup /dev/drbd0 show
disk {
size 0s _is_default; # bytes
on-io-error detach;
fencing dont-care _is_default;
no-disk-flushes ;
no-md-flushes ;
max-bio-bvecs 0 _is_default;
}
net {
timeout 60 _is_default; # 1/10 seconds
max-epoch-size 2048 _is_default;
max-buffers 2048 _is_default;
unplug-watermark 128 _is_default;
connect-int 10 _is_default; # seconds
ping-int 10 _is_default; # seconds
sndbuf-size 131070 _is_default; # bytes
ko-count 0 _is_default;
after-sb-0pri discard-least-changes;
after-sb-1pri violently-as0p;
after-sb-2pri violently-as0p;
rr-conflict disconnect _is_default;
ping-timeout 5 _is_default; # 1/10 seconds
}
syncer {
rate 12288k; # bytes/second
after -1 _is_default;
al-extents 127 _is_default;
verify-alg "";
}
protocol C;
_this_host {
device "/dev/drbd0";
disk "/dev/part4";
meta-disk internal;
address 172.16.32.13:7788;
}
_remote_host {
address 172.16.32.9:7788;
}
---------------------------------------------------
drbd IO configuration on a SLES11_SP2 installation:
---------------------------------------------------
# drbdsetup /dev/drbd0 show
disk {
size 0s _is_default; # bytes
on-io-error detach;
fencing dont-care _is_default;
no-disk-flushes ;
no-md-flushes ;
max-bio-bvecs 0 _is_default;
disk-timeout 0 _is_default; # 1/10 seconds
}
net {
timeout 60 _is_default; # 1/10 seconds
max-epoch-size 2048 _is_default;
max-buffers 2048 _is_default;
unplug-watermark 128 _is_default;
connect-int 10 _is_default; # seconds
ping-int 10 _is_default; # seconds
sndbuf-size 0 _is_default; # bytes
rcvbuf-size 0 _is_default; # bytes
ko-count 0 _is_default;
after-sb-0pri discard-least-changes;
after-sb-1pri violently-as0p;
after-sb-2pri violently-as0p;
rr-conflict disconnect _is_default;
ping-timeout 5 _is_default; # 1/10 seconds
on-congestion block _is_default;
congestion-fill 0s _is_default; # byte
congestion-extents 127 _is_default;
}
syncer {
rate 12288k; # bytes/second
after -1 _is_default;
al-extents 127 _is_default;
on-no-data-accessible io-error _is_default;
c-plan-ahead 0 _is_default; # 1/10 seconds
c-delay-target 10 _is_default; # 1/10 seconds
c-fill-target 0s _is_default; # bytes
c-max-rate 102400k _is_default; # bytes/second
c-min-rate 4096k _is_default; # bytes/second
}
protocol C;
_this_host {
device minor 0;
disk "/dev/part4";
meta-disk internal;
address ipv4 172.16.0.13:7788;
}
_remote_host {
address ipv4 172.16.0.9:7788;
}
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