Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
> Hi all:
>
> I have no idea about how long the primary sync its data to secondary?
>
> Or once the data is changed on primary physical device, it is send to
> secondary immediately?
Data replication is basically real-time, within the constraints of network
bandwidth and raw I/O performance.
In the "resource" section of /etc/drbd.conf, you define the transfer protocol
to use for that resource (/dev/drbd0 for example).
It can be one of the following three:
C: write IO is reported as completed, if we know it has
reached _both_ local and remote DISK.
* for critical transactional data.
B: write IO is reported as completed, if it has reached
local DISK and remote buffer cache.
* for most cases.
A: write IO is reported as completed, if it has reached
local DISK and local tcp send buffer. (see also sndbuf-size)
* for high latency networks
If you choose C, then write a file to the DRBD'd filesystem, the write won't
return (ie: the command won't complete) until the data is written to both
local and remote disks.
Mark.
--
Mark Watts BSc RHCE MBCS
Senior Systems Engineer
QinetiQ Trusted Information Management
Trusted Solutions and Services Group
GPG Key: http://keyserver.veridis.com:11371/search?q=0x455420ED
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