[DRBD-user] Sync speed (getting to the limit)

[Marcelo Pereira]

Hi DRBD masters,

I have been trying to push the sync speed to the limit, as the server was
offline for a while and I will release it for general use only after it's
sync'ed. So, nobody is using and I can use full speed.

I have two servers, each one connected to a NAS unit through a CAT6 cable,
no switches in between. It's 1000 Mpbs full duplex, as the ethtool says.

I tried to push to the limit, issuing the following:

[~]# /sbin/drbdsetup /dev/drbd0 syncer -r 685M

I can't go beyond 685M, as it says it's not a valid parameter (from 686 and
beyond).

And then the /proc/drbd looks like it:

*node0: Primary*

version: 8.3.12 (api:88/proto:86-96)
GIT-hash: e2a8ef4656be026bbae540305fcb998a5991090f build by
mockbuild at builder10.centos.org, 2012-01-28 13:52:25
 0: cs:SyncSource ro:Primary/Secondary ds:UpToDate/Inconsistent C r-----
    ns:576775776 nr:0 dw:108 dr:576798277 al:3 bm:166274 lo:26 pe:57 ua:64
ap:0 ep:1 wo:b oos:4171057976
 [>....................] sync'ed:  0.9% (4073296/4106360)M
finish: 16:14:21 speed: 71,340 (64,984) K/sec

*node1: Secondary*

version: 8.3.12 (api:88/proto:86-96)
GIT-hash: e2a8ef4656be026bbae540305fcb998a5991090f build by
mockbuild at builder10.centos.org, 2012-01-28 13:52:40
 0: cs:SyncTarget ro:Secondary/Primary ds:Inconsistent/UpToDate C r-----
    ns:0 nr:33272320 dw:33272320 dr:0 al:0 bm:2031 lo:1 pe:7421 ua:0 ap:0
ep:1 wo:b oos:4171642808
 [>....................] sync'ed:  0.8% (4073868/4106360)M
finish: 16:13:46 speed: 71,384 (64,856) want: 701,440 K/sec

At this point, it is going dramatically fast, as the original configuration
(10M) was forecasting 190 hours to sync... (16h, in this case, is a charm).
How can I know if it's the faster it can go???

Thanks,
Marcelo
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