[DRBD-user] drbd storage size

Meij, Henk hmeij at wesleyan.edu
Thu Oct 23 15:57:31 CEST 2014

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

Thanks for the write up y'll.  I'll have to think about #3 not sure I grasp it fully.

Last night I started a 12 TB test and started first initialization for observation (0 is primary).
I have node0:eth1 wired directly into node1:eth1 with 10 foot CAT 6 cable (MTU=9000)
Data from node1 to node0
PING ( 8970(8998) bytes of data.
8978 bytes from icmp_seq=1 ttl=64 time=0.316 ms

This morning's progress report from node1:(drbd v8.4.5)

        [===>................] sync'ed: 21.7% (8847740/11287100)M
        finish: 62:50:50 speed: 40,032 (39,008) want: 68,840 K/sec

which confuses me: 8.8M out of 11.3M is 77.8% synced, not? I will let this test finish before I do a dd attempt.

iostat reveals %idle cpu 99%+ and little to no %iowait (near 0%), iotop confirms very little IO (<5 K/s), typical data
Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sdb1              0.00   231.00    0.00  156.33     0.00 79194.67   506.58     0.46    2.94   1.49  23.37

Something is throttling this IO as 40M/s is about half of what I was hoping for. Will dig some more.


From: drbd-user-bounces at lists.linbit.com [drbd-user-bounces at lists.linbit.com] on behalf of Philipp Reisner [philipp.reisner at linbit.com]
Sent: Thursday, October 23, 2014 9:17 AM
To: drbd-user at lists.linbit.com
Subject: Re: [DRBD-user] drbd storage size

Am Donnerstag, 23. Oktober 2014, 08:55:03 schrieb Digimer:
> On 23/10/14 04:00 AM, Philipp Reisner wrote:
> > 2a) Initialize both backend devices to a known state.
> >
> >      I.e. dd if=/dev/zero of=/dev/sdb1 bs=$((1024*1024)) oflag=direct
> Question;
>    What I've done in the past to speed up initial sync is to create the
> DRBD device, pause-sync, then do your 'dd if=/dev/zero ...' trick to
> /dev/drbd0. This effectively drives the resync speed to the max possible
> and ensures full sync across both nodes. Is this a sane approach?

Yes, sure that is a way to do it. (I have the impression that is something
form the drbd-8.3 world.)

I do not know from the top of the head if that will be faster than the
built-in background resync in drbd-8.4.


drbd-user mailing list
drbd-user at lists.linbit.com

More information about the drbd-user mailing list