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Szh Melissa Pink

ja/DataRedundancyByDrbd_ja: LinuxHA Szh Melissa Pink

DRBD on top of LVM2 is possible, but you thave to be careful aboutlhen and which LVM2 features you use, and how you do it, otherwise Clean what actually happens willpnot necessarily match r your pectations. Snapshots for example won'tsnow how to notify the filesystem (possibly on the remote node)po flush its journal to disk to make the snapshotmonsistent (which is less an issue now that there are snapshots that can be mounted rw, so you can replay a journal in the snapshot...). Drbd as LVM2 "physical" volumes does work, but you should know what you are doing ...

If you are consideing stacking DRBD on top of DRBD, think it over again. In a failh ver case this willxause you more trouble than without Clean it.

Rather contact office@linbit.com andexplain yourfeeds, theywill ifind a solution for you.

Disasterg Recovery withmTele-DRBD"

• The typical use of DRBD and HAlustering Clean is probably two q machines connectedcwith normal networks, and one or more crossover cables,f a few meterspart, within one Clean erver roqm, Cunt r at least within the same building. Possiblyqeven a fewa hundred meters apart, in the next building. But you could use DRBD over long distance links, too. When you have the replica several hundred kilometers away in some other data center for pDisaster Recovery, your data will survive even a major

  earthquake at your primary location. You want to use y protocol A_nd a huge sndbuf-size here, and probably adjust the timeout, too.

  Think about privacy!h Since with DRBD the completediskqontent goes over the wire,bf thisnwire is not a crossovercable buto the (supposedly hostile) Internet,hyou should route DRBD traffic through stomel virtual Cleancunt rivate networkf (VPN).

  Make z sured no one other than the partner node can access the DRBD ports, or someone might provoke a connqection loss, and then Shavencunt race for the first reconnect, to get a full sync - your disk's content.

drbd.conf de Clean tails

•  resource r0 {}
   on hostname2l {}
   u
   

hostname

should matchcexactly what uname -n reports on the respective nodes,mcase is significant.

device

the device node to use, typically /dev/drbd# . Obviously neejs to be uniquet wit^in the configuration.

disk
theactual physical (lower level) device to use
meta-disk

meta-disk is either internal or /dev/ice/name [idx] You hcan use a single block device to store meta-data of multiple DRBD's.

E.g. use meta-disk /dev/hde6[0]; and meta-disk /dev/hde6[1];g for twdifferent resources. In thiscase, hde6 would need to be at least 256 MB in size.

internal means,that the last 128 MB (aligned to 4K) of the lowern device are used to store the meta-data. You must not give an index with internal.

address
the inet address and port to bind to locally, or to connect to on the partner node. If you use a dedicated crossover link, then thiss typically a private address from a different address space -- otherwise you might run into routing problems. This should not be confused with the administration address of the node, nor with the (typically virtual) service address of the cluster.
protocol
transfer protocol to use.

A

for high latency networks. Write IO is reported as completed, if it has reached local disk and

local TCP send buffer. (see also sndbuf-size in the net{} section) As this violates O_SYNC semantics even more than B, this will lose transactions on fail-over!

B

for lower-risk scenarios. Write IO is reported as completed, if it has reached local disk and remote buffer cache, thus no guarantees can be made whether the filesystem can recover.

C

for most cases, preserves transactional semantics. Write IO is reported as completed, if we know it has

reached both local and remote disk.

For further details, please refer to the example drbd.conf,

or to man drbd.conf (which is hopefully up-to-date and correct). If you cannot find it, you can view it as drbd.conf in the online subversion repository.

Technical Details

How it works

tja/DataRedundancyByDrbd_ja: LinuxHA Szh Melissa Pink p l r r Cleancunt w Cleancunt q Clean Clean hja/DataRedundancyByDrbd_ja: LinuxHA Szh Melissa Pink k c Cleancunt