[DRBD-user] A few configuration questions specific to RHEL 5 primary/primary GFS2 setup

Kushnir, Michael (NIH/NLM/LHC) [C] michael.kushnir at nih.gov
Wed Oct 12 17:17:13 CEST 2011

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

Good morning,

I am running a two node DRBD 8.3.8 primary/primary cluster with GFS2 on RHEL 5.7. GFS2 is exported via GNBD. My underlying hardware is 2 x Dell C2100 server with LSI 9260-8i RAID controllers. RAID set is RAID10 with 10 x 1TB SATA 7.2k disks. I use 1MB stripe size as well as read and write caching. NIC is dual-port Myri 10GbE (10G-PCIE2-8B2-S2) connected to Cisco M4900. Ports are in LACP group. 

My questions:

1. In the case of a 2-primary split brain (switch hiccup, etc), I would like server #1 to always remain primary and server #2 to always shut down. I would like this behavior because server #2 can't become secondary because GNBD is not going to release it. What is the best way to accomplish this?

2. I've tried the deadline queue manager as well as CFQ. I've noticed no difference. Can you please elaborate on why deadline is better, and how can I measure any performance difference between the two?

3. It seems that GNBD is the biggest source of latency in my system. It decreases IOPS by over ~50% (based on DD tests compared to the same DRBD based GFS2 mounted locally). I've also tried Enterprise iSCSI target as an alternative and the results were not much better. The latency on my LAN is ~0.22ms. Can you offer any tuning tips?


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