Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
I have a doubt not just ... I'll explain better
I have this situation, implemented with CentOS 5.5 x86_64:
two nodes, each node has a raid controller with BBU, two network interface
bonding round-robin with dedicated cables
I set up the raid array like this:
sda1 / boot
sda2 /
sda3 swap
sda5 - just partition (disk drbd)
I configure drbd with dual primary and with the usual protocol C
use other parameters to improve performance:
common {
syncer {rate 100M;}
}
...
disk {
on-io-error detach;
use-bmbv;
no-disk-flushes;
no-md-flushes;
}
....
net {
timeout 60; # 6 seconds (unit = 0.1 seconds)
connect-int 10, # 10 seconds (unit = 1 second)
ping-int 10, # 10 seconds (unit = 1 second)
ping-timeout 5; # 500 ms (unit = 0.1 seconds)
max-buffers 2048;
unplug-watermark 128;
max-epoch-size 2048;
ko-count 5;
allow-two-primaries;
after-sb-0pri disconnect;
after-sb-1pri disconnect;
after-sb-2pri disconnect;
rr-conflict disconnect;
}
...
syncer {
rate 100M;
al-extents 257;
}
...
on node1 {
device /dev/drbd0;
disk /dev/disk/by-id/scsi-3600605b0014416401257a2af36d89bfc-part5;
address 10.0.42.251:7788;
meta-disk internal;
}
on node2 {
device /dev/drbd0;
disk /dev/disk/by-id/scsi-3600605b0014403f0125c874d21c5521d-part5;
address 10.0.42.252:7788;
meta-disk internal;
}
if I check the status of drbd the following response is:
0: cs: Connected ro: Primary/Primary ds: UpToDate/UpToDate C r ----
ns: 640864680 nr: 135234784 dw: 776099464 dr: 1520599328 al: 836478 bm:
2185 lo: 0 pe: 0 ua: 0 ap: 0 ep: 1 wo: b OOS: 0
I do not know if it is positive that the to write after write method is
Barrier .... reading the manuals of drbd I noticed that in these cases (BBU)
performance would be better for a wo:n
What do you think?
more to this I can tell you that another hardware configuration with a
simple SATA disks in software raid 0 configuration (sda and sdb) and
without drbd.conf options: no-disk-flushes -no-md-flushes, The drbd uses
instead the drain ... that seems to be dangerous without a BBU, but the drbd
has preferred this choice, and not clear to me ...
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