[DRBD-user] slow sync speed

Schmidt, Florian florian.schmidt at centric-it.de
Mon Jul 21 15:30:14 CEST 2008

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

Hello everybody,

I have a drbd-setup with 4 volumes with alltogether 40GB of capacity.

The machines are connected via crossover-cable. Both NICs are GbE
I set the speed in the drbd.conf to 600M because with larger values he
complaints, but I think 600M should be OK.

Well the problem is: sync is really slow:

cat /proc/drbd
version: 8.2.6 (api:88/proto:86-88)
GIT-hash: 3e69822d3bb4920a8c1bfdf7d647169eba7d2eb4 build by
buildsvn at c5-i386-build, 2008-06-02 10:17:29
 0: cs:SyncSource st:Secondary/Primary ds:UpToDate/Inconsistent C r---
    ns:1882668 nr:17308 dw:17308 dr:1890692 al:0 bm:137 lo:1 pe:78
ua:251 ap:0 oos:17661984
        [>...................] sync'ed:  9.7% (17248/19084)M
        finish: 1:45:07 speed: 2,640 (1,768) K/sec
 1: cs:SyncSource st:Secondary/Primary ds:UpToDate/Inconsistent C r---
    ns:1884704 nr:4 dw:4 dr:2354048 al:0 bm:114 lo:1 pe:124 ua:14667
ap:0 oos:7894416
        [==>.................] sync'ed: 19.3% (7709/9546)M
        finish: 0:54:49 speed: 2,356 (1,768) K/sec
 2: cs:SyncSource st:Secondary/Primary ds:UpToDate/Inconsistent C r---
    ns:1888356 nr:216 dw:216 dr:1896928 al:0 bm:118 lo:1 pe:70 ua:268
ap:0 oos:7889040
        [==>.................] sync'ed: 19.4% (7704/9546)M
        finish: 0:32:52 speed: 3,872 (1,776) K/sec
 3: cs:Connected st:Secondary/Primary ds:UpToDate/UpToDate C r---
    ns:987896 nr:160 dw:160 dr:987896 al:0 bm:61 lo:0 pe:0 ua:0 ap:0

I know syncing all drbd-volumes at the same time isn't a very good idea,
but shouldn't the speed normally be a little faster?

On the sync-target top prints this:
Cpu(s):  0.5%us,  0.2%sy,  0.0%ni, 99.0%id,  0.0%wa,  0.0%hi,  0.3%si,

but on the sync-source this:
Cpu(s):  0.5%us,  0.5%sy,  0.0%ni,  0.0%id, 98.2%wa,  0.2%hi,  0.7%si,

So the problem is somehow the sync-source?

I have internal metadata. Could this be the problem?

Thanks in advance

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