[DRBD-user] drbd 0.7.4 half the speed of 0.6.13

Philipp Reisner philipp.reisner at linbit.com
Mon Sep 20 11:56:02 CEST 2004

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

> I've tried a plethora of different max-buffers / max-epoch values,
> starting with 2048/2048, and ending up at 256/256 as this improved
> performance from about 20MB/sec to about 28MB/sec. Still no where near
> the 73MB/sec I can reliably obtain using 0.60.13

Lars already posted the patch that should fix this issue (please
report success or no success, so that we can include this patch
into the next upstream release)
And I really want that drbd-0.7 will sync at least as fast as drbd-0.6.

On the other hand I want to point out that a lower sync rate should
not be a real issue. drbd-0.7 will only sync the amount of data covered
by the AL, while drbd-0.6 will sync the whole device after a primary
crash. This gives that drbd-0.7 will finish the sync process faster
than drbd-0.6 anyway (if your device is considerabely bigger than the
area covered by AL).

> Please help! I'd like to be able to take advantage of the added benefits
> of 0.7.x, but this is for a DB server that is already I/O constrained...
> I can't afford to take this kind of performance hit.

Just to make it more clear. This "sync performance" only applies to 
the resync process (and you should _constrain_ it to _not_ use 100%
of your overall IO performance). It does not affect the perfomance 
during normal mirroring operation (cs: connected)

: Dipl-Ing Philipp Reisner                      Tel +43-1-8178292-50 :
: LINBIT Information Technologies GmbH          Fax +43-1-8178292-82 :
: Schönbrunnerstr 244, 1120 Vienna, Austria    http://www.linbit.com :

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