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Install and configure DRDB for network filesystem replication on Debian 8


Let’s talk about Network Filesystem Replication.

Network filesystem replication is often used today in many scenarios:

  • Replication of a filesystem for security reasons: if one node fails, the other node is accessible.
  • To replicate a filesystem to another company headquarter, so each emplyee has access to his data locally and not through a public network. But if he goes to the other headquarter he has all his data, and again he can access locally.

As you can imagine, this kind of system is often used to build filesystems for cluster environment.

We have chosen to implement the solution with DRDB. It’s main porpouse is (as other systems like this) High Availability and Disaster Recovery for file systems.

We implement the solution with Debian 8, but it should work also on Ubuntu.

Prerequisites

Before we start, here are the prerequisites:

  • At least 2 Debian servers.
  • Debian is installed as a minimal installation (not necessary at all if you know what are you doing on production systems) recommended guide https://www.Kreationnext.com/tutorial/debian-8-jessie-minimal-server/
  • At least 2 Linux disks in each server: /dev/sda for the linux installation, /dev/sdb for the DRDB installation.

ATTENTION!!!: During installation, all data on disk /dev/sdb will be destroyed, so don’t work on a disk with data inside.

DRBD Installation

In our example, I will use two nodes, wich are:

  • 192.168.152.100 mysql1.local.vm
  • 192.168.152.110 mysql2.local.vm

On all nodes, modify the file /etc/hosts as follows:

127.0.0.1 localhost
192.168.152.100 mysql1.local.vm mysql1
192.168.152.110 mysql2.local.vm mysql2

# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Then execute the following commands to install DRDB:

apt-get update
apt-get -y upgrade
apt-get install drbd-utils

Configuration Primary/Secondary – Disaster Recovery

The main configuration file is /etc/drbd.conf wich looks like the following one:

include “drbd.d/global_common.conf”;
include “drbd.d/*.res”;

By convention, /etc/drbd.d/global_common.conf contains the global and common sections of the DRBD configuration, whereas the .res files contain one resource in each section.

In our example we do a minimal setup that replicates the data on the two nodes. On each node do the following modification:

We’ll start editing the file /etc/drbd.d/global_common.conf modify the default line from

global {
usage-count yes;
# minor-count dialog-refresh disable-ip-verification
}

net {
protocol C;
# protocol timeout max-epoch-size max-buffers unplug-watermark
# connect-int ping-int sndbuf-size rcvbuf-size ko-count
# allow-two-primaries cram-hmac-alg shared-secret after-sb-0pri
# after-sb-1pri after-sb-2pri always-asbp rr-conflict
# ping-timeout data-integrity-alg tcp-cork on-congestion
# congestion-fill congestion-extents csums-alg verify-alg
# use-rle
}

Now we’ll create the configuration file /etc/drbd.d/r0.res for our resource. Create the file on all nodes and add this inside:

resource r0 {
  on mysql1.local.vm {
    device    /dev/drbd1;
    disk      /dev/sdb;
    address   192.168.152.100:7789;
    meta-disk internal;
  }
  on mysql2.local.vm {
    device    /dev/drbd1;
    disk      /dev/sdb;
    address   192.168.152.110:7789;
    meta-disk internal;
  }
}

What we have done until now is the following:

  • You “opt in” to be included in DRBD’s usage statistics with  usage-count parameter.
  • Resources are configured to use fully synchronous replication with Protocol Cunless explicitly specified otherwise.
  • Our cluster consists of two nodes: mysql1 and mysql2.
  • We have a resource arbitrarily named r0 which uses /dev/sdb as the lower-level device, and is configured with internal meta data.
  • The resource uses TCP port 7789 for its network connections, and binds to the IP addresses 192.168.152.100 and 192.168.152.110 respectively.

On all nodes initialize the metadata with the following command:

drbdadm create-md r0

You should see something like this:

–== Thank you for participating in the global usage survey ==–
The server’s response is:

you are the 2963th user to install this version
initializing activity log
NOT initializing bitmap
Writing meta data…
New drbd meta data block successfully created.
success

Next, we enable the resource and initialize the first replication run, only on first node, it should start replicating:

drbdadm up r0
drbdadm primary --force r0

To check if all is working well you can check the file /proc/drbd on both nodes and you shold see something like this:

Mysql1

root@mysql1:# cat /proc/drbd
version: 8.4.3 (api:1/proto:86-101)
srcversion: 1A9F77B1CA5FF92235C2213
1: cs:SyncSource ro:Primary/Secondary ds:UpToDate/Inconsistent C r—–
ns:54624 nr:0 dw:0 dr:55536 al:0 bm:3 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:5188060
[>………………..] sync’ed: 1.1% (5064/5116)Mfinish: 0:17:21 speed: 4,964 (4,964) K/sec

Mysql2 

root@mysql2:# cat /proc/drbd
version: 8.4.3 (api:1/proto:86-101)
srcversion: 1A9F77B1CA5FF92235C2213
1: cs:SyncTarget ro:Secondary/Primary ds:Inconsistent/UpToDate C r—–
ns:0 nr:17496 dw:17496 dr:0 al:0 bm:1 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:5225188
[>………………..] sync’ed: 0.4% (5100/5116)Mfinish: 0:29:41 speed: 2,916 (2,916) want: 5,160 K/sec

During the build phase you can notice the UpToDate/Inconsistent, it’s correct because this is the first sync of data.

After the filsystem is synced this shloud change to UpToDate/UpToDate like in the following log:

root@mysql1:/home/sysop# cat /proc/drbd
version: 8.4.3 (api:1/proto:86-101)
srcversion: 1A9F77B1CA5FF92235C2213
1: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r—–
ns:5242684 nr:0 dw:0 dr:5243596 al:0 bm:320 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0

Now we have a new block device, called /dev/drbd1 that we can format with our preferred filesystem type. For example, if we want to format it in ext4 and mount it on /var/www we can simply do:

root@mysql1:/home/sysop# mkfs.ext4 /dev/drbd1
mke2fs 1.42.12 (29-Aug-2014)
Creazione del file system con 1310671 4k blocchi e 327680 inode
Etichetta del file system=ab3e18c9-e8cb-42c8-977a-ab79bdb18aea
Backup del superblocco salvati nei blocchi:
32768, 98304, 163840, 229376, 294912, 819200, 884736
Allocating group tables: fatto
Scrittura delle tavole degli inode: fatto
Creating journal (32768 blocks): fatto
Scrittura delle informazioni dei super-blocchi e dell’accounting del file system: fatto

Then we can mount our filesystem:

mkdir /var/www
mount /dev/drbd1 /var/www

The /var/www directory is now mounted through the drbd system.

In this scenario, with a Primary/Secondary configuration, we have implemented a disaster recovery system.

In this case, if you try to mount the filesystem on the second node, you’ll get an error:

root@mysql2:~# mount /dev/drbd1 /var/www/
mount: /dev/drbd1 is write-protected, mounting read-only
mount: mount /dev/drbd1 on /var/www failed: Tipo di supporto errato

This is normal and expected because of our configuration.

Now we can simluate a fail on mysql1, so power it down with poweroff command.

On mysql2 we can see what heappens:

Oct 5 13:52:14 mysql2 kernel: [13458.629215] drbd r0: PingAck did not arrive in time.
Oct 5 13:52:14 mysql2 kernel: [13458.629587] drbd r0: peer( Primary -> Unknown ) conn( Connected -> NetworkFailure ) pdsk( UpToDate -> DUnknown )
Oct 5 13:52:14 mysql2 kernel: [13458.629919] drbd r0: asender terminated
Oct 5 13:52:14 mysql2 kernel: [13458.629921] drbd r0: Terminating drbd_a_r0
Oct 5 13:52:14 mysql2 kernel: [13458.630028] drbd r0: Connection closed
Oct 5 13:52:14 mysql2 kernel: [13458.630035] drbd r0: conn( NetworkFailure -> Unconnected )
Oct 5 13:52:14 mysql2 kernel: [13458.630035] drbd r0: receiver terminated
Oct 5 13:52:14 mysql2 kernel: [13458.630036] drbd r0: Restarting receiver thread
Oct 5 13:52:14 mysql2 kernel: [13458.630037] drbd r0: receiver (re)started
Oct 5 13:52:14 mysql2 kernel: [13458.630041] drbd r0: conn( Unconnected -> WFConnection )

The mysql2 node detects that mysql1 is dead, and if we check the /proc/drbd:

root@mysql2:~# cat /proc/drbd
version: 8.4.3 (api:1/proto:86-101)
srcversion: 1A9F77B1CA5FF92235C2213
1: cs:WFConnection ro:Secondary/Unknown ds:UpToDate/DUnknown C r—–
ns:0 nr:5457236 dw:5457236 dr:0 al:0 bm:320 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0

we can see the status changed from Secondary/primary to Secondary/unknown. So now we do the trick, promoting mysql2 as primary. On mysql2 simply run:

drbdadm primary r0

let’s check again /proc/drbd and see the magic…

root@mysql2:~# cat /proc/drbd
version: 8.4.3 (api:1/proto:86-101)
srcversion: 1A9F77B1CA5FF92235C2213
1: cs:WFConnection ro:Primary/Unknown ds:UpToDate/DUnknown C r—–
ns:0 nr:5457236 dw:5457236 dr:912 al:0 bm:320 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0

As you can see our node now is primary and can be regularly mounted.

root@mysql2:~# mount /dev/drbd1 /var/www/
root@mysql2:~# df -h
File system Dim. Usati Dispon. Uso% Montato su
/dev/sda1 9,3G 1,4G 7,5G 16% /
udev 10M 0 10M 0% /dev
tmpfs 97M 4,6M 92M 5% /run
tmpfs 241M 0 241M 0% /dev/shm
tmpfs 5,0M 4,0K 5,0M 1% /run/lock
tmpfs 241M 0 241M 0% /sys/fs/cgroup
/dev/drbd1 4,8G 10M 4,6G 1% /var/www

Now we assume we wanna take up mysql1 again, if we start now we’ll come to split brain, infact you can check log and see these errors:

Oct 5 14:26:04 mysql1 kernel: [ 7.760588] drbd r0: conn( StandAlone -> Unconnected )
Oct 5 14:26:04 mysql1 kernel: [ 7.760599] drbd r0: Starting receiver thread (from drbd_w_r0 [458])
Oct 5 14:26:04 mysql1 drbdadm[435]: adjust net: r0
Oct 5 14:26:04 mysql1 drbdadm[435]: ]
Oct 5 14:26:04 mysql1 kernel: [ 7.769318] drbd r0: receiver (re)started
Oct 5 14:26:04 mysql1 kernel: [ 7.769327] drbd r0: conn( Unconnected -> WFConnection )
Oct 5 14:26:04 mysql1 /etc/init.d/mysql[485]: MySQL PID not found, pid_file detected/guessed: /var/run/mysqld/mysqld.pid
Oct 5 14:26:04 mysql1 acpid: starting up with netlink and the input layer
Oct 5 14:26:04 mysql1 acpid: 1 rule loaded
Oct 5 14:26:04 mysql1 acpid: waiting for events: event logging is off
Oct 5 14:26:05 mysql1 kernel: [ 8.270578] drbd r0: Handshake successful: Agreed network protocol version 101
Oct 5 14:26:05 mysql1 kernel: [ 8.270581] drbd r0: Agreed to support TRIM on protocol level
Oct 5 14:26:05 mysql1 kernel: [ 8.270770] drbd r0: conn( WFConnection -> WFReportParams )
Oct 5 14:26:05 mysql1 kernel: [ 8.270771] drbd r0: Starting asender thread (from drbd_r_r0 [461])
Oct 5 14:26:05 mysql1 kernel: [ 8.272594] block drbd1: drbd_sync_handshake:
Oct 5 14:26:05 mysql1 kernel: [ 8.272597] block drbd1: self 242B364F4A5B9C68:525CC995A3CFBA2B:44A1DE193A6C6701:0000000000000004 bits:64463 flags:0
Oct 5 14:26:05 mysql1 kernel: [ 8.272598] block drbd1: peer 6903F6042F95F5FF:525CC995A3CFBA2A:44A1DE193A6C6700:0000000000000004 bits:4 flags:0
Oct 5 14:26:05 mysql1 kernel: [ 8.272599] block drbd1: uuid_compare()=100 by rule 90
Oct 5 14:26:05 mysql1 kernel: [ 8.272601] block drbd1: helper command: /sbin/drbdadm initial-split-brain minor-1
Oct 5 14:26:05 mysql1 kernel: [ 8.272692] drbd r0: meta connection shut down by peer.
Oct 5 14:26:05 mysql1 kernel: [ 8.272720] drbd r0: conn( WFReportParams -> NetworkFailure )
Oct 5 14:26:05 mysql1 kernel: [ 8.272722] drbd r0: asender terminated
Oct 5 14:26:05 mysql1 kernel: [ 8.272722] drbd r0: Terminating drbd_a_r0
Oct 5 14:26:05 mysql1 kernel: [ 8.279158] block drbd1: helper command: /sbin/drbdadm initial-split-brain minor-1 exit code 0 (0x0)
Oct 5 14:26:05 mysql1 kernel: [ 8.279173] block drbd1: Split-Brain detected but unresolved, dropping connection!
Oct 5 14:26:05 mysql1 kernel: [ 8.279197] block drbd1: helper command: /sbin/drbdadm split-brain minor-1
Oct 5 14:26:05 mysql1 kernel: [ 8.286125] block drbd1: helper command: /sbin/drbdadm split-brain minor-1 exit code 0 (0x0)
Oct 5 14:26:05 mysql1 kernel: [ 8.286144] drbd r0: conn( NetworkFailure -> Disconnecting )
Oct 5 14:26:05 mysql1 kernel: [ 8.286146] drbd r0: error receiving ReportState, e: -5 l: 0!
Oct 5 14:26:05 mysql1 kernel: [ 8.287009] drbd r0: Connection closed
Oct 5 14:26:05 mysql1 kernel: [ 8.287017] drbd r0: conn( Disconnecting -> StandAlone )
Oct 5 14:26:05 mysql1 kernel: [ 8.287018] drbd r0: receiver terminated
Oct 5 14:26:05 mysql1 kernel: [ 8.287019] drbd r0: Terminating drbd_r_r0

This is because, now we have two primary nodes, that is not possibile in a Primary/Secondary configuration. So assuming fresh data id on mysql2, we have to demote mysql1 to Secondary.

So on mysql1 run:

root@mysql1:~# drbdadm secondary r0
root@mysql1:~# drbdadm connect –discard-my-data r0

On mysql2 instead, wich is the split brain survivor, we have to execute:

root@mysql2:~# drbdadm connect r0

now you can check and see that all is rebuilding correctly, but now mysql1 is secondary and mysql2 is primary.

root@mysql1:~# cat /proc/drbd
version: 8.4.3 (api:1/proto:86-101)
srcversion: 1A9F77B1CA5FF92235C2213
1: cs:SyncTarget ro:Secondary/Primary ds:Inconsistent/UpToDate C r—–
ns:0 nr:28224 dw:28224 dr:0 al:0 bm:1 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:229628
[=>………………] sync’ed: 11.2% (229628/257852)K
finish: 0:01:04 speed: 3,528 (3,528) want: 6,600 K/sec

DRBD Configuration as Primary/Primary cluster for High Availability

Now we want to configure our Network Filesystem Cluster to work in a High Availability configuration. For that, we have to make some changes to the configuration.

Edit the configuration file /etc/drbd.d/r0.res and add the red configurations:

resource r0 {
on mysql1.local.vm {
device /dev/drbd1;
disk /dev/sdb;
address 192.168.152.100:7789;
meta-disk internal;
}
on mysql2.local.vm {
device /dev/drbd1;
disk /dev/sdb;
address 192.168.152.110:7789;
meta-disk internal;
}
handlers {
split-brain “/usr/lib/drbd/notify-split-brain.sh root”;
}
net {
allow-two-primaries;
after-sb-0pri discard-zero-changes;
after-sb-1pri discard-secondary;
after-sb-2pri disconnect;
}
startup {
become-primary-on both;
}
}

In detail, we have automated the managment of a split brain situation, because we are in a HA environment, and fail over must be automated.

split-brain = this is the action to be taken when splitbrain heappens, in this case, he sends an email to root@localhost.

after-sb-0pri = Split brain has just been detected, but at this time the resource is not in the Primary role on any host.

discard-zero-changes = If there is any host on which no changes occurred at all, simply apply all modifications made on the other and continue.
after-sb-1pri = Split brain has just been detected, and at this time the resource is in the Primary role on one host.

discard-secondary = Whichever host is currently in the Secondary role, make that host the split brain victim.

after-sb-2pri = Split brain has just been detected, and at this time the resource is in the Primary role on both hosts.

Then on both servers run the following commands, each command on each server simultaneously:

drbdadm disconnect r0
drbdadm connect r0
drbdadm primary r0

Then restart service on both servers with:

/etc/init.d/drbd restart

Now if we look at logs of drbd for both nodes we can see

root@mysql1:~# cat /proc/drbd
version: 8.4.3 (api:1/proto:86-101)
srcversion: 1A9F77B1CA5FF92235C2213
1: cs:Connected ro:Primary/Primary ds:UpToDate/UpToDate C r—–
ns:0 nr:12 dw:4 dr:904 al:0 bm:1 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0

root@mysql2:~# cat /proc/drbd
version: 8.4.3 (api:1/proto:86-101)
srcversion: 1A9F77B1CA5FF92235C2213
1: cs:Connected ro:Primary/Primary ds:UpToDate/UpToDate C r—–
ns:12 nr:0 dw:0 dr:924 al:0 bm:1 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0

As you can see, in both cases the configuration is Primary/Primary, so now you can mount the partion on both servers if needed.

root@mysql1:~# mount /dev/drbd1 /var/www/
root@mysql1:~# df -h
File system Dim. Usati Dispon. Uso% Montato su
/dev/sda1 9,3G 1,4G 7,5G 16% /
udev 10M 0 10M 0% /dev
tmpfs 97M 4,6M 92M 5% /run
tmpfs 241M 0 241M 0% /dev/shm
tmpfs 5,0M 4,0K 5,0M 1% /run/lock
tmpfs 241M 0 241M 0% /sys/fs/cgroup
/dev/drbd1 4,8G 10M 4,6G 1% /var/www

Now check how it works. Try to create one file in mysql1

root@mysql1:~# touch /var/www/mysql1.txt
root@mysql1:~#

And now try mount drbd1 on mysql2 and see if mysql1.txt is present.

root@mysql2:~# mount /dev/drbd1 /var/www/
root@mysql2:~# ls -al /var/www/
totale 24
drwxr-xr-x 3 root root 4096 ott 5 15:30 .
drwxr-xr-x 12 root root 4096 ott 5 12:26 ..
drwx—— 2 root root 16384 ott 5 12:23 lost+found
-rw-r–r– 1 root root 0 ott 5 15:20 mysql1.txt

As you can see, the file is present!

DRDB with OCFS2 filesystem

In the previous scenario there’s a little problem: if you mount both filesystems, you can’t see the changes, until you remount the partition, and this in some situation may be a problem, so instead of ext4, you can use ocfs2 filesystem.

First of all be sure to have /dev/drbd1 unmounted, so for security on both servers, run:

umount /var/www

Now we install the ocfs2 utilities on both nodes to create our distributed filesystem:

apt-get install ocfs2-tools

After that, we can create the ocfs2 filesystem with the command:

root@mysql1:/var/www# mkfs -t ocfs2 -N 2 -L ocfs2_drbd1 /dev/drbd1

The output should be something similare to this:

root@mysql1:/var/www# mkfs -t ocfs2 -N 2 -L ocfs2_drbd1 /dev/drbd1
mkfs.ocfs2 1.6.4
Cluster stack: classic o2cb
/dev/drbd1 is mounted; will not make a ocfs2 volume here!
root@mysql1:/var/www# cd
root@mysql1:~# umount /var/www/
root@mysql1:~# mkfs -t ocfs2 -N 2 -L ocfs2_drbd1 /dev/drbd1
mkfs.ocfs2 1.6.4
Cluster stack: classic o2cb
Label: ocfs2_drbd1
Features: sparse backup-super unwritten inline-data strict-journal-super xattr
Block size: 4096 (12 bits)
Cluster size: 4096 (12 bits)
Volume size: 5368508416 (1310671 clusters) (1310671 blocks)
Cluster groups: 41 (tail covers 20431 clusters, rest cover 32256 clusters)
Extent allocator size: 4194304 (1 groups)
Journal size: 67108864
Node slots: 2
Creating bitmaps: done
Initializing superblock: done
Writing system files: done
Writing superblock: done
Writing backup superblock: 2 block(s)
Formatting Journals: done
Growing extent allocator: done
Formatting slot map: done
Formatting quota files: done
Writing lost+found: done
mkfs.ocfs2 successful

Now we use the native features of ocfs2 to manage the distributed filesystem.

Let’s start edit /etc/ocfs2/cluster.conf on boths node and add the following:

node:
ip_port = 7777
ip_address = 192.168.152.100
number = 0
name = mysql1.local.vm
cluster = ocfs2
node:
ip_port = 7777
ip_address = 192.168.152.110
number = 1
name = mysql2.local.vm
cluster = ocfs2
cluster:
node_count = 2
name = ocfs2

We have to restart the ocfs2 service. Run on both nodes this command:

/etc/init.d/o2cb restart

And check the status is ok like this:

root@mysql1:~# /etc/init.d/o2cb status
* o2cb.service – LSB: Load O2CB cluster services at system boot.
Loaded: loaded (/etc/init.d/o2cb)
Active: active (exited) since Wed 2016-10-05 16:10:20 CEST; 23s ago
Process: 2767 ExecStop=/etc/init.d/o2cb stop (code=exited, status=0/SUCCESS)
Process: 2793 ExecStart=/etc/init.d/o2cb start (code=exited, status=0/SUCCESS)
Oct 05 16:10:20 mysql1.local.vm systemd[1]: Starting LSB: Load O2CB cluster services at system boot….
Oct 05 16:10:20 mysql1.local.vm o2cb[2793]: Loading filesystem “configfs”: OK
Oct 05 16:10:20 mysql1.local.vm o2cb[2793]: Loading stack plugin “o2cb”: OK
Oct 05 16:10:20 mysql1.local.vm o2cb[2793]: Loading filesystem “ocfs2_dlmfs”: OK
Oct 05 16:10:20 mysql1.local.vm o2cb[2793]: Creating directory ‘/dlm’: OK
Oct 05 16:10:20 mysql1.local.vm o2cb[2793]: Mounting ocfs2_dlmfs filesystem at /dlm: OK
Oct 05 16:10:20 mysql1.local.vm o2cb[2793]: Setting cluster stack “o2cb”: OK
Oct 05 16:10:20 mysql1.local.vm o2cb[2793]: Starting O2CB cluster ocfs2: OK
Oct 05 16:10:20 mysql1.local.vm systemd[1]: Started LSB: Load O2CB cluster services at system boot..

And now you can do the magic and mount disk on both servers:

root@mysql1:~# mount -t ocfs2 /dev/drbd1 /var/www/

root@mysql2:~# mount -t ocfs2 /dev/drbd1 /var/www/

And try to create the file on both servers:

root@mysql1:~# touch /var/www/mysql1.txt

root@mysql2:~# touch /var/www/mysql2.txt

You can check that you see both files:

root@mysql1:~# ls -al /var/www/
totale 4
drwxr-xr-x 3 root root 3896 ott 5 16:20 .
drwxr-xr-x 12 root root 4096 ott 5 12:25 ..
drwxr-xr-x 2 root root 3896 ott 5 15:55 lost+found
-rw-r–r– 1 root root 0 ott 5 16:20 mysql1.txt
-rw-r–r– 1 root root 0 ott 5 16:20 mysql2.txt

root@mysql2:~# ls -al /var/www/
totale 4
drwxr-xr-x 3 root root 3896 ott 5 16:20 .
drwxr-xr-x 12 root root 4096 ott 5 12:26 ..
drwxr-xr-x 2 root root 3896 ott 5 15:55 lost+found
-rw-r–r– 1 root root 0 ott 5 16:20 mysql1.txt
-rw-r–r– 1 root root 0 ott 5 16:20 mysql2.txt

Performance

You can do some performance tests to check the speed of the configuration. In my case, i’ll get those results with a virtual machine on my PC. On a real server, the speed will be much higher.

First, install ioping, to test the performance on random read.

apt-get install ioping

Then run the test:

root@mysql1:cd /var/www
root@mysql1:/var/www# ioping -R .
— . (ocfs2 /dev/drbd1) ioping statistics —
49.3 k requests completed in 3.00 s, 17.1 k iops, 66.7 MiB/s
min/avg/max/mdev = 43 us / 58 us / 8.41 ms / 64 us

66,7 MiB/s on a random read is very very good result!!

And a sequential read:

root@mysql1:/var/www# dd if=/dev/zero of=test bs=64k count=32k conv=fdatasync
32768+0 record dentro
32768+0 record fuori
2147483648 byte (2,1 GB) copiati, 34,1095 s, 63,0 MB/s

Conclusion

This tutorial could be the basis for a mirror setup of ISPConfig, create different drdb resources for /var/www and /var/vmail, should work very ver fast.

Best Practices

  • For a filesystem with a high traffic volume, use at least a dedicated network cards.
  • For network failover bond togheter at least 2 network interfaces.
  • DRBD has a lot of options to tune the configuration and the performance of nodes.

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