Have you test these values ?
https://drbd.linbit.com/users-guide/s-throughput-tuning.html
El 26/05/15 a las 13:16, Ben RUBSON escribió:
RAID controller is OK yes.
Here is a 4 steps example of the issue :
### 1 - initial state :
Source :
- sdb read MB/s : 0
- sdb write MB/s : 0
- eth1 incoming MB/s : 0
- eth1 outgoing MB/s : 0
Target :
- sdb read MB/s : 0
- sdb write MB/s : 0
- eth1 incoming MB/s : 0
- eth1 outgoing MB/s : 0
### 2 - dd if=/dev/zero of=bigfile :
Source :
- sdb read MB/s : 0
- sdb write MB/s : 670
- eth1 incoming MB/s : 1
- eth1 outgoing MB/s : 670
Target :
- sdb read MB/s : 0
- sdb write MB/s : 670
- eth1 incoming MB/s : 670
- eth1 outgoing MB/s : 1
### 3 - disable the link between the 2 nodes :
Source :
- sdb read MB/s : 0
- sdb write MB/s : 670
- eth1 incoming MB/s : 0
- eth1 outgoing MB/s : 0
Target :
- sdb read MB/s : 0
- sdb write MB/s : 0
- eth1 incoming MB/s : 0
- eth1 outgoing MB/s : 0
### 4 - re-enable the link between the 2 nodes :
Source :
- sdb read MB/s : ~20
- sdb write MB/s : ~670
- eth1 incoming MB/s : 1
- eth1 outgoing MB/s : 670
Target :
- sdb read MB/s : 0
- sdb write MB/s : 670
- eth1 incoming MB/s : 670
- eth1 outgoing MB/s : 1
DRBD resource :
1: cs:SyncTarget ro:Secondary/Primary ds:Inconsistent/UpToDate C r-----
ns:62950732 nr:1143320132 dw:1206271712 dr:1379744185 al:9869
bm:6499 lo:2 pe:681 ua:1 ap:0 ep:1 wo:d oos:11883000
[>...................] sync'ed: 6.9% (11604/12448)M
finish: 0:34:22 speed: 5,756 (6,568) want: 696,320 K/sec
### values I would have expected in step 4 :
Source :
- sdb read MB/s : ~400 (because of c-min-rate 400M)
- sdb write MB/s : ~370
- eth1 incoming MB/s : 1
- eth1 outgoing MB/s : 670
Target :
- sdb read MB/s : 0
- sdb write MB/s : 670
- eth1 incoming MB/s : 670
- eth1 outgoing MB/s : 1
Why resync is totally ignored and application (dd here in the example)
still consumes all available IOs / bandwidth ?
Thank you,
Ben
2015-05-25 16:50 GMT+02:00 A.Rubio <[email protected]
<mailto:[email protected]>>:
Cache settings an I/O in RAID controller is optimal ???
Write-back, write-through, cache enablad, I/O direct, ...
El 25/05/15 a las 11:50, Ben RUBSON escribió:
The link between nodes is a 10Gb/s link.
The DRBD resource is a RAID-10 array which is able to resync
at up to 800M (as you can see I have lowered it to 680M in my
configuration file).
The "issue" here seems to be a prioritization "issue" between
application IOs and resync IOs.
Perhaps I miss-configured something ?
Goal is to have resync rate up to 680M, with a minimum of
400M, even if there are application IOs.
This in order to be sure to complete the resync even if there
are a lot of write IOs from the application.
With my simple test below, this is not the case, dd still
writes at its best throughput, lowering resync rate which
can’t reach 400M at all.
Thank you !
Le 25 mai 2015 à 11:18, A.Rubio <[email protected]
<mailto:[email protected]>> a écrit :
the link between nodes is ??? 1Gb/s ??? , 10Gb/s ??? ...
the Hard Disks are ??? SATA 7200rpm ???, 10000rpm ???, SAS
???,
SSD ???...
400M to 680M with a 10Gb/s link and SAS 15.000 rpm is OK
but less ...
Le 12 avr. 2014 à 17:23, Ben RUBSON
<[email protected] <mailto:[email protected]>> a
écrit :
Hello,
Let's assume the following configuration :
disk {
c-plan-ahead 0;
resync-rate 680M;
c-min-rate 400M;
}
Both nodes are uptodate, and on the primary, I have a
test IO burst running, using dd.
I then cut replication link for a few minutes so that
secondary node will be several GB behind primary node.
I then re-enable replication link.
What I expect here according to the configuration is
that secondary node will fetch missing GB at a 400
MB/s throughput.
DRBD should then prefer resync IOs over application
(dd here) IOs.
However, it does not seems to work.
dd still writes at its best throughput, meanwhile
reads are made from the primary disk between 30 and 60
MB/s to complete the resync.
Of course this is not the expected behaviour.
Did I miss something ?
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