drbd online verify stalls (DRBD OPENAIS)
This document (7009306) is provided subject to the disclaimer at the end of this document.
SUSE Linux Enterprise Server 11 Service Pack 1
On systems with a very high performance, especially if coupled with a high sync rate this online verify can actually result in a stalled verify. This is characterized by checkin /proc/drbd and getting a result similar to
version: 8.3.11 (api:88/proto:86-96)
GIT-hash: 0de839cee13a4160eed6037c4bddd066645e23c5 build by phil@fat-tyre,
0: cs:VerifyS ro:Primary/Secondary ds:UpToDate/UpToDate C r-----
ns:5232620 nr:0 dw:2224 dr:5357005 al:43 bm:319 lo:2 pe:174462 ua:8192 ap:1
ep:1 wo:d oos:0
[>....................] verified: 1.9% (5016/5104)M
finish: 2:54:50 speed: 488 (488) want: 307,200 K/sec
where the values for pe (pending) and ua (unacknowledged) rise accompanied by entries in /var/log/messages like
Aug 26 12:22:51 mercury kernel: [ 2599.550987] block drbd0: [drbd0_worker/3155] sock_sendmsg time expired, ko = 4294966875
where max-buffers is increased to 128k, the maximum. And sndbuf-size and rcvbuf-size are drastically increased. The value has to be determined by testing, 4M could be considered a starting point.
then in syncer the static rate is replaced by dynamical c-plan-ahead, c-min-rate, c-max-rate. and c-fill-target. Where c-min-rate is the minimum syncer rate, c-max-rate the old static value and c-fill-target could be half of the above, in the net section set, sndbuf-size and rcvbuf-size. As with these this value is best determined by testing, a starting point could be 2M.
The dynamical sync rate is available since drbd version 8.3.10
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- Document ID:7009306
- Creation Date:07-SEP-11
- Modified Date:27-APR-12
- SUSESUSE Linux Enterprise Server