[DRBD-user] DRBD performance - disk random access time problem

Proskurin Kirill proskurin-kv at fxclub.org
Mon May 31 14:09:53 CEST 2010

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


Hello.

Software:
Debian Lenny 2.6.26-2-amd64
ocfs2-tools 1.4.1-1
drbd8-2.6.26-2-amd64  2:8.3.7-1~bpo50+1+2.6.26-21lenny4
drbd8-source          2:8.3.7-1~bpo50+1
drbd8-utils           2:8.3.7-1~bpo50+1

Hardware:
Dell server
Adaptec 5405 RAID Controller (write cache enabled)
2x1TB 7200rpm HDD


I make some test for disk random access time and it is horrible:

# ./seeker /dev/drbd0
Seeker v2.0, 2007-01-15, 
http://www.linuxinsight.com/how_fast_is_your_disk.html
Benchmarking /dev/drbd0 [858643MB], wait 30 
seconds..............................
Results: 65 seeks/second, 15.26 ms random access time

While linear speed is good.
# hdparm -Tt /dev/drbd0

/dev/drbd0:
  Timing cached reads:   13928 MB in  2.00 seconds = 6972.83 MB/sec
  Timing buffered disk reads:  628 MB in  3.01 seconds = 208.82 MB/sec

Whats wrong with seek time? How can I tune\fix it?

Seeks on non DRBD partition is more good:

Results: 129 seeks/second, 7.71 ms random access time




My drbd conf:

# cat /etc/drbd.d/global_common.conf
global {
	usage-count yes;
}

common {
	protocol C;

	handlers {
		pri-on-incon-degr "/usr/lib/drbd/notify-pri-on-incon-degr.sh; 
/usr/lib/drbd/notify-emergency-reboot.sh; echo b > /proc/sysrq-trigger ; 
reboot -f";
		pri-lost-after-sb "/usr/lib/drbd/notify-pri-lost-after-sb.sh; 
/usr/lib/drbd/notify-emergency-reboot.sh; echo b > /proc/sysrq-trigger ; 
reboot -f";
		local-io-error "/usr/lib/drbd/notify-io-error.sh; 
/usr/lib/drbd/notify-emergency-shutdown.sh; echo o > /proc/sysrq-trigger 
; halt -f";
		outdate-peer "/usr/lib/heartbeat/drbd-peer-outdater -t 5";
			}

	startup {
		wfc-timeout 60;
		degr-wfc-timeout 30;
		outdated-wfc-timeout 15;
		become-primary-on both;
		}

	disk {
		fencing resource-and-stonith;
		no-disk-flushes;
		no-md-flushes;
		}

	net {
		cram-hmac-alg sha1;
		shared-secret "password";
		allow-two-primaries;
		ping-timeout 20;
                 after-sb-0pri discard-zero-changes;
                 after-sb-1pri discard-secondary;
                 after-sb-2pri disconnect;
		}

	syncer {
		rate 100M;
		}
}

# cat /etc/drbd.d/drbd0.res
resource drbd0 {

on server1.domain.org {
device /dev/drbd0;
disk /dev/sda9;
address 192.168.1.1:7789;
meta-disk internal;
}

on server2.domain.org {
device /dev/drbd0;
disk /dev/sda9;
address 192.168.1.2:7789;
meta-disk internal;
}

  }


-- 
С уважением,
Проскурин Кирилл



More information about the drbd-user mailing list