[DRBD-user] Identifying High iowait on DRBD Computers

bart.coninckx at telenet.be bart.coninckx at telenet.be
Thu Feb 17 17:24:14 CET 2011

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


Eric, 

some things that come to mind: 

- have you verified with iotop what is using the I/O? 
- or both nodes up to date? No sync running? 
- in case of protocol C: issue with the network connection? Failed bonding cards? Drop of NIC speed? 

B. 


----- "Eric Robinson" <eric.robinson at psmnv.com> schreef: 
> 
> This iowait thing is driving me batty. The system was running fine for a long time at about 1-7% iowait except during backups. During backups iowait is usually pegged at 25%. But recently, the system has started running at 25% iowait all the time , with periods of 50% iowait and peaks of 70-90%. This is a relatively sudden development. 
> 
> The server is 4-core PowerEdge 2950 with 8GB of RAM and 6x300GB 7.5K SAS drives in a RAID 5 array. All it does is FTP. It peaks at about 250 concurrent FTP users. Average file size is about 80K. The backing device for drbd0 is a 2TB LVM partition. The filesystem is ext3. Since kjournald is the biggest consumer of disk iops, I will soon change the filesystem to mount with 'noatime'. 
> 
> Any ideas? Is there something about using LVM+drbd+ext3 with a 2TB partition (1.3TB used) that causes a sudden jump in disk wait? 


-- 
> Eric Robinson 
> 




























> 
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