Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi Emmanuel,
Try the following settings in global_common.conf ?
common {
disk {
c-plan-ahead 0;
resync-rate 800M;
}
}
Regards,
Ben
> Le 2 déc. 2015 à 17:48, Emmanuel Florac <eflorac at intellique.com> a écrit :
>
>
>
> I've set up a pair of identical servers with RAID arrays (8 cores, 16GB
> RAM, 12x2 TB RAID6), 3 10GigE interfaces, to host some highly available
> services.
>
> The systems are currently running Debian 7.9 Wheezy oldstable (because
> corosync/pacemaker are not available on 8.x stable nor testing).
> However I've tried with Jessie too, no dice.
>
> Local disk performance is about 900 MB/s write, 1600 MB/s read. network
> throughput between the machines is over 700MB/s. through iSCSI, each
> machine can write to the other's storage at more than 700 MB/s.
>
> However, no matter the way I configure DRBD, the throughput is limited
> to 100MB/s. It really looks like some hardcoded limit. I can reliably
> lower performance by tweaking the settings, but it never goes over
> 1Gbit (122MB/s are reached for a couple of seconds at a time). I'm
> really pulling my hair on this one.
>
> plain vanilla kernel 3.18.24 amd64
> drbd 8.9.2~rc1-1~bpo70+1
>
> The configuration is split in two files: global-common.conf:
>
> global {
> usage-count no;
> }
>
> common {
> handlers {
> }
>
> startup {
> }
>
> disk {
> on-io-error detach;
> # no-disk-flushes ;
> }
> net {
> max-epoch-size 8192; # tried some values,
> max-buffers 8192; # no real difference
> sndbuf-size 2097152;# or lower perf.
> }
> syncer {
> rate 4194304k; # changing this does
> # nothing much
> al-extents 6433;
> }
> }
>
> and cluster.res:
>
> resource rd0 {
> protocol C;
> on cl1 {
> device /dev/drbd0;
> disk /dev/sda4;
> address 192.168.42.1:7788;
> meta-disk internal;
> }
>
> on cl2 {
> device /dev/drbd0;
> disk /dev/sda4;
> address 192.168.42.2:7788;
> meta-disk internal;
> }
> }
>
> Output from cat /proc/drbd on slave :
>
> version: 8.4.5 (api:1/proto:86-101)
> srcversion: EDE19BAA3D4D4A0BEFD8CDE
> 0: cs:SyncTarget ro:Secondary/Secondary ds:Inconsistent/UpToDate C
> r----- ns:0 nr:4462592 dw:4462592 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0
> ep:1 wo:f oos:16489499884 [>....................] sync'ed: 0.1%
> (16103024/16107384)M finish: 49:20:03 speed: 92,828 (92,968) want:
> 102,400 K/sec
>
> Output from vmstat 2 on master (both machines are almost completely
> idle):
>
> procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 0 0 0 14952768 108712 446108 0 0 213 254 16 9 0 0 100 0
> 0 0 0 14952484 108712 446136 0 0 0 4 10063 1361 0 0 99 0
> 0 0 0 14952608 108712 446136 0 0 0 4 10057 1356 0 0 99 0
> 0 0 0 14952608 108720 446128 0 0 0 10 10063 1352 0 1 99 0
> 0 0 0 14951616 108720 446136 0 0 0 6 10175 1417 0 1 99 0
> 0 0 0 14951748 108720 446136 0 0 0 4 10172 1426 0 1 99 0
>
>
> Output from iperf between the two servers:
>
> ------------------------------------------------------------
> Client connecting to cl2, TCP port 5001
> TCP window size: 325 KByte (default)
> ------------------------------------------------------------
> [ 3] local 192.168.42.1 port 47900 connected with 192.168.42.2 port
> 5001 [ ID] Interval Transfer Bandwidth
> [ 3] 0.0-10.0 sec 6.87 GBytes 5.90 Gbits/sec
>
> Apparently initial synchronisation is supposed to be somewhat slow, but
> not this slow... Furthermore it doesn't really react to any attempt to
> throttle sync rate like
>
> drbdadm disk-options --resync-rate=800M all
>
> I've tried setting up an md mirror of the 2 volumes over iSCSI on these
> machines (cl1 using cl2 as a target), works just fine (mirror
> synchronizes in about 6 hours, performance is 80% of local). So there's
> obviously nothing wrong with the network and RAID stacks (even if the
> network throughput is somewhat low for some reason).
>
> --
> ------------------------------------------------------------------------
> Emmanuel Florac | Direction technique
> | Intellique
> | <eflorac at intellique.com>
> | +33 1 78 94 84 02
> ------------------------------------------------------------------------
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