[DRBD-user] Documentation Bug?

James Dingwall james.dingwall at zynstra.com
Wed Jun 11 15:44:19 CEST 2014

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


If I have understood how the meta-data space is allocated then I believe 
I have found a documentation bug in in 

|meta-disk internal|, |meta-disk /|device|/|, |meta-disk /|device|/ 

    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.

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