[DRBD-user] drbdmeta dump-md output missing the AL ?

Robert reg at elconas.de
Wed Oct 1 10:41:51 CEST 2008

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

Hello list,

the drbdmeta command states that the the dump-md command returns the 
activity log also:


Dumps the whole contents of the meta data storage including the stored 
bit-map and activity-log, in a textual representation.

However, where can the AL be found in the output of dump-md ?

# DRBD meta data dump
# 2008-10-01 10:34:27 +0200 [1222850067]
# irdbt-vm02> drbdmeta --force /dev/drbd0 v08 /dev/vg00/drbd0 internal 

version "v08";

# md_size_sect 3856
# md_offset 63417872384
# al_offset 63417839616
# bm_offset 63415902208

uuid {
0xF16C42FEE61D07A2; 0x0000000000000000; 0x5E61E3733808DD22; 
flags 0x00000015;
la-size-sect 123859184;
bm-byte-per-bit 4096;
device-uuid 0x14DD281B87D190C0;
# bm-bytes 1935304;
bm {
# at 0kB
241920 times 0x0000000000000000;
# bits-set 0;

As far as I see this, bm is the quikc sync bitmap.

Where's the AL ?

And one more question regarding the AL:

The DRBD Manual states:
As DRBD detects write I/O on a disconnected device, and hence starts 
setting bits in the quick-sync bitmap, it does so in RAM — thus avoiding 
expensive synchronous metadata I/O operations. Only when the 
corresponding blocks turn cold (that is, expire from the Activity Log 
<http://www.drbd.org/users-guide/s-activity-log.html>), DRBD makes the 
appropriate modifications in an on-disk representation of the quick-sync 
bitmap. Likewise, if the resource happens to be manually shut down on 
the remaining node while disconnected, DRBD flushes the /complete/ 
quick-sync bitmap out to persistent storage.

The interesting part is [...] Only when the corresponding blocks turn 
cold (that is, expire from the Activity Log 
<http://www.drbd.org/users-guide/s-activity-log.html>) [...]

Does the AL Extend turn cold ONLY if the nuber of open AL Extends is 
reached and a AL Extend has to be reused (so to speak LRU) (I have 
written so much data on disk, that all configured al-extend are used and 
I have to write to a block that is not covered by a AL Extend yet) or 
does the AL also expire AL Extend based on a timeout mechanism (so to 
speak LRU+timeout) (e.g. a AL Extend not written to in 5 seconds is 


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