[DRBD-user] syncer performance problem

Jeff Buck jeffb at umci.com
Fri Jul 30 19:59:50 CEST 2004

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


On Thu, 2004-07-29 at 15:11, Jeff Buck wrote:

> If we scp a large file from one machine to another, we get about 20-30
> MB/sec through the dedicated gigabit network link, but our sync speed
> seems stuck right around 2.8 MB/sec. We get slightly better
> performance

With huge files, scp settles in at 18.5 megs a second.

I've now tried changing the drbd settings to the point I think we've got
pretty absurd settings, but still can't really note any speed change.

I've pulled wires to make sure that drbd is routing through the correct
interfaces. I got a nice clean connection lost, and reconnection. There
aren't any strange messages in the logs anywhere.

There is no activity on the drive other than the sync (most of the time
it has actually been unmounted).

I remember reading a while back that some cards or drives don't like to
sync in a certain direction and performance would drop considerably.. I
can't seem to find anything about that now, but could it be something
like that? I couldn't find any configuration options to change the sync
direction.

Could it be that it doesn't like the size of the volume? I would expect
that plenty of other people on this list have volumes that large though
(1.4 Terabytes).

I noticed that the block count in drbd changed by quite a bit when we
went to running reiserfs on the volume instead of running lvm2. Seemed
kinda strange, but I was guessing that reiser just doubled the block
size and drbd saw that. The sync speed remained constant the entire
time, and the filesystem on top had the correct amount of space each
time.

Some of my configuration info:

 0: cs:SyncSource st:Primary/Secondary ld:Consistent
    ns:160688580 nr:0 dw:1036740 dr:159695336 al:505 bm:9744 lo:0
pe:1278 ua:0 ap:0
        [===================>] sync'ed: 98.9% (459782/615687)M
        finish: 44:19:59 speed: 2,920 (2,774) K/sec


 0: cs:SyncTarget st:Secondary/Primary ld:Inconsistent
    ns:0 nr:169578088 dw:169578084 dr:0 al:0 bm:10286 lo:139 pe:1239
ua:139 ap:0
        [===================>] sync'ed: 97.6% (451097/615687)M
        finish: 45:30:02 speed: 2,811 (2,771) K/sec


[root at nupiter root]# mount
/dev/nb0 on /data type reiserfs (rw)
[root at nupiter root]# df -h /data
Filesystem            Size  Used Avail Use% Mounted on
/dev/nb0              1.4T  1.1G  1.4T   1% /data

Lower device: 08:04   (sda4)
Meta device: internal
Disk options:
 on-io-error = detach
Local address: 192.168.0.1:7788
Remote address: 192.168.0.2:7788
Wire protocol: B
Net options:
 timeout = 6.0 sec (default)
 connect-int = 10 sec (default)
 ping-int = 10 sec (default)
 max-epoch-size = 524288
 max-buffers = 524288
 sndbuf-size = 33554432
 ko-count = 0  (default)
Syncer options:
 rate = 20480 KB/sec
 group = 1
 al-extents = 521








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