Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi,
If I have understood how the meta-data space is allocated then I believe
I have found a documentation bug in in
http://www.drbd.org/users-guide/re-drbdconf.html:
|meta-disk internal|, |meta-disk /|device|/|, |meta-disk /|device|/
[/|index|/]|
Internal means that the last part of the backing device is used to
store the meta-data. The size of the meta-data is computed based on
the size of the device.
When a /|device|/ is specified, either with or without an /|index|/,
DRBD stores the meta-data on this device. Without /|index|/, the
size of the meta-data is determined by the size of the data device.
This is usually used with LVM, which allows to have many variable
sized block devices. The meta-data size is 36kB +
Backing-Storage-size / 32k, rounded up to the next 4kb boundary.
(Rule of the thumb: 32kByte per 1GByte of storage, rounded up to the
next MB.)
When an /|index|/ is specified, each index number refers to a fixed
slot of meta-data of 128 MB, which allows a maximum data size of 4
GB. This way, multiple DBRD devices can share the same meta-data
device. For example, if /dev/sde6[0] and /dev/sde6[1] are used,
/dev/sde6 must be at least 256 MB big. Because of the hard size
limit, use of meta-disk indexes is discouraged.
For indexed meta-data slots should that be 4TB instead of 4GB? 128 MB
contains 4096 32kB units, if each unit can back 1GB data then this is 4TB.
Thanks,
James
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