[DRBD-user] High IOwait with rsync on DRBD-OCFS2-NFS node

Prater, James K. jprater at draper.com
Sun Jan 5 16:03:02 CET 2014

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

Most likely will require you to rebuild the volumes with lvm (clustered version) in the middle (rawdev>lvm>drbd>ocfs) then take a lvm snapshot, back that up.  The snapshot should be static and not updated, point in time.  However keep in mind,  it you read excessively from the shared device, you will slow everything down.    A better approach is to have each client backup their own little world, there can schedule such a way not to saturate the I/O capability of the storage system.

Just a suggestion


----- Original Message -----
From: Vasily S. Kostroma [mailto:admin at v-sf.info]
Sent: Friday, January 03, 2014 07:04 PM
To: drbd-user at lists.linbit.com <drbd-user at lists.linbit.com>
Subject: [DRBD-user] High IOwait with rsync on DRBD-OCFS2-NFS node

Happy holidays, friends.
It's my first message in this list.

I have two 100% same servers with two logical drives - one for system 
and second one for DRBD primary-primary configuration. The servers 
connected via dedicated Gb NIC's via crossover cable. Operational system 
is Debian 7, file system for DRBD is OCFS2. Additionally I using NFS 
server to share a files from DRBD drive to other servers. The 
configuration is very simple. Just one resource with internal metadata. 
Nothing special.

But I have a problem and, unfortunately, I have no idea how to fix it.
I using Node1 as primary and Node2 as secondary. I mean clients 
(web-servers) are connecting to Node1 via NFS, and backup's running on 
Node2. Example. I starting rsync on Node2 to sync a local folder with 
folder on the same server, but DRBD+OCFS2. It's working fine, but in 
backup time the NFS server on Node1 stop working till backup on Node2 is 
in progress. A NFS processes (threads) is on "D" state in top. After 
backups completed the NFS start working perfectly. Just for additional 
attention: I running rsync on Node2, but NFS stop working on Node1.

I will appreciate any idea what is wrong.. All settings is almost 
default, but problem is there :(

Sorry for my English.
And thank you in advance.
Happy holidays!

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