<div dir="ltr"><div style="font-family:arial,sans-serif;font-size:13px"><div>dd if=/dev/zero of=./testbin bs=512 count=1000 oflag=direct<br></div><div>12000 bytes (512 kB) copied, 0.153541 s, 3.3 MB/s</div><div><br></div>
</div><div style="font-family:arial,sans-serif;font-size:13px">This was run against /root/testbin which is <span style="font-family:arial;font-size:small">/dev/md1</span><span style="font-family:arial;font-size:small"> with no LVM or DRBD</span></div>
<div style="font-family:arial,sans-serif;font-size:13px"><span style="font-family:arial;font-size:small"><br></span></div>
<div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px">dd if=/dev/zero of=./testbin bs=512 count=1000 oflag=direct<br>
512000 bytes (512 kB) copied, 32.3254 s, 15.8 kB/s<br></div><div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px">This was run against /mnt/tmp which is DRBD <span style="font-family:arial;font-size:small">/dev/drbd2 </span>backed by an LVM logical volume, with the logical volume backed by /dev/md127 while /dev/drbd2 was in the connected state</div>
<div style="font-family:arial,sans-serif;font-size:13px"><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Jun 5, 2014 at 9:24 AM, Digimer <span dir="ltr"><<a href="mailto:lists@alteeve.ca" target="_blank">lists@alteeve.ca</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I use iperf for network testing.<br>
<br>
Those dd's are run on the machine directly with the HDDs attached, not over the network connection? It's also direct to the backing device, not through /dev/drbdX? If so, your storage is the problem.<div class="">
<br>
<br>
On 05/06/14 01:51 AM, Bret Mette wrote:<br>
</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="">
Do you have any suggestions on how I can test the network in isolation<br>
that would yield results helpful in this scenario?<br>
<br>
DRBD was not syncing, as I got those results even with the secondary in<br>
disconnect. Storage directly yields the following results:<br>
<br>
node1<br>
dd if=/dev/zero of=./testbin bs=512 count=1000 oflag=direct<br>
12000 bytes (512 kB) copied, 0.153541 s, 3.3 MB/s<br>
<br>
node2<br>
dd if=/dev/zero of=~/testbin bs=512 count=1000 oflag=direct<br>
512000 bytes (512 kB) copied, 0.864994 s, 592 kB/s<br>
512000 bytes (512 kB) copied, 0.328994 s, 1.6 MB/<br>
<br>
<br>
On Wed, Jun 4, 2014 at 10:35 PM, Digimer <<a href="mailto:lists@alteeve.ca" target="_blank">lists@alteeve.ca</a><br></div><div><div class="h5">
<mailto:<a href="mailto:lists@alteeve.ca" target="_blank">lists@alteeve.ca</a>>> wrote:<br>
<br>
On 04/06/14 11:31 AM, Bret Mette wrote:<br>
<br>
Hello,<br>
<br>
I started looking at DRBD as a HA ISCSI target. I am<br>
experiencing very<br>
poor performance and decided to run some tests. My current setup<br>
is as<br>
follows:<br>
<br>
Intel(R) Xeon(R) CPU E3-1230 V2 @ 3.30GH<br>
CentoS 6.5 - 2.6.32-431.17.1.el6.x86_64<br>
drbd version: 8.3.16 (api:88/proto:86-97)<br>
md RAID10 using 7200rpm drives<br>
<br>
The 2 drbd nodes are synced using an intel 82579LM Gigabit card<br>
<br>
I have created an logical drive using LVM and configured a<br>
couple drbd<br>
resources on top of that. drbd0 is my iscsi configuration file,<br>
which is<br>
shared between the 2 nodes and drbd1 is a 1.75TB ISCSI target.<br>
<br>
I run heartbeat on the two nodes and expose a virtual IP to the<br>
ISCSI<br>
initiators.<br>
<br>
Originally I was running ISCSI with write-cache off (for data<br>
integrity<br>
reasons) but have recently switched to write-cache on during testing<br>
(with little to no gain).<br>
<br>
My major concern is the extremely high latency test results I<br>
got when<br>
when dd against drbd0 mounted on the primary node.<br>
<br>
dd if=/dev/zero of=./testbin bs=512 count=1000 oflag=direct<br>
512000 bytes (512 kB) copied, 32.3254 s, 15.8 kB/s<br>
<br>
I have pinged the second node as a very basic network latency<br>
test and<br>
get 0.209ms response time. I have also run the same test on both<br>
nodes<br>
with drbd disconnected (or on partitions not associated with<br>
drbd) and<br>
get typical results:<br>
<br>
node1<br>
dd if=/dev/zero of=./testbin bs=512 count=1000 oflag=direct<br>
12000 bytes (512 kB) copied, 0.153541 s, 3.3 MB/s<br>
<br>
node2<br>
dd if=/dev/zero of=~/testbin bs=512 count=1000 oflag=direct<br>
512000 bytes (512 kB) copied, 0.864994 s, 592 kB/s<br>
512000 bytes (512 kB) copied, 0.328994 s, 1.6 MB/s<br>
<br>
node2's latency (without drbd connected) is inconsistent but always<br>
falls between those two ranges.<br>
<br>
These tests were run with no ISCSI targets exposed, no initiators<br>
connected, essentially on an idle system.<br>
<br>
My question is why are my drbd connected latency tests showing<br>
results<br>
35 to 100 times slower than my results when dbrd is not<br>
connected (or<br>
against partitions not backed by drbd)?<br>
<br>
This seems to be the source of my horrible performance on the ISCSI<br>
targs (300~900 K/sec dd writes on the initiators) and very high<br>
iowait<br>
(35-75%) on mildly busy initiators.<br>
<br>
<br>
Any advice pointers, etc. would be highly appreciated. I have<br>
already<br>
tried numerous performance tuning settings (suggested by the drbd<br>
manual). But I am open to any suggestion and will try anything<br>
again if<br>
it might solve my problem.<br>
<br>
Here are the important bits of my current drbd.conf<br>
<br>
net {<br>
cram-hmac-alg sha1;<br>
shared-secret "password";<br>
after-sb-0pri disconnect;<br>
after-sb-1pri disconnect;<br>
after-sb-2pri disconnect;<br>
rr-conflict disconnect;<br>
max-buffers 8000;<br>
max-epoch-size 8000;<br>
sndbuf-size 0;<br>
}<br>
<br>
syncer {<br>
rate 100M;<br>
verify-alg sha1;<br>
al-extents 3389;<br>
}<br>
<br>
I've played with the watermark setting and a few others and<br>
latency only<br>
seems to get worse or stay where it's at.<br>
<br>
<br>
Thank you,<br>
Bret<br>
<br>
<br>
Have you tried testing the network in isolation? Is the DRBD<br>
resource syncing? With a syncer rate of 100M on a 1 Gbps NIC, that's<br>
just about all your bandwidth consumed by background sync. Can you<br>
test the speed of the storage directly, not over iSCSI/network?<br>
<br>
--<br>
Digimer<br>
Papers and Projects: <a href="https://alteeve.ca/w/" target="_blank">https://alteeve.ca/w/</a><br>
What if the cure for cancer is trapped in the mind of a person<br>
without access to education?<br>
<br>
<br>
</div></div></blockquote><div class="HOEnZb"><div class="h5">
<br>
<br>
-- <br>
Digimer<br>
Papers and Projects: <a href="https://alteeve.ca/w/" target="_blank">https://alteeve.ca/w/</a><br>
What if the cure for cancer is trapped in the mind of a person without access to education?<br>
</div></div></blockquote></div><br></div>