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List:       drbd-user
Subject:    Re: [DRBD-user] drbd storage size
From:       "Meij, Henk" <hmeij () wesleyan ! edu>
Date:       2014-10-23 13:57:31
Message-ID: 8688BD11DAC0574AA90295127E9E9F4AC046CC48 () exchangewes8 ! wesad ! wesleyan ! edu
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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 10.10.52.232 (10.10.52.232) 8970(8998) bytes of data.
8978 bytes from 10.10.52.232: 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.

-Henk

________________________________________
From: drbd-user-bounces@lists.linbit.com [drbd-user-bounces@lists.linbit.com] on \
                behalf of Philipp Reisner [philipp.reisner@linbit.com]
Sent: Thursday, October 23, 2014 9:17 AM
To: drbd-user@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.

Best,
 Phil

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