Thanks Somnath.

I am running with CentOS7.2.  Have you seen this pattern before?

- epk

From: Somnath Roy [mailto:somnath....@sandisk.com]
Sent: Tuesday, July 26, 2016 4:44 PM
To: EP Komarla <ep.koma...@flextronics.com>; ceph-users@lists.ceph.com
Subject: RE: Ceph performance pattern

Which OS/kernel you are running with ?
Try setting bigger read_ahead_kb for sequential runs.

Thanks & Regards
Somnath

From: ceph-users [mailto:ceph-users-boun...@lists.ceph.com] On Behalf Of EP 
Komarla
Sent: Tuesday, July 26, 2016 4:38 PM
To: ceph-users@lists.ceph.com<mailto:ceph-users@lists.ceph.com>
Subject: [ceph-users] Ceph performance pattern

Hi,

I am showing below fio results for Sequential Read on my Ceph cluster.  I am 
trying to understand this pattern:

- why there is a dip in the performance for block sizes 32k-256k?
- is this an expected performance graph?
- have you seen this kind of pattern before

[cid:image001.png@01D1E75D.B0A2F760]

My cluster details:
Ceph: Hammer release
Cluster: 6 nodes (dual Intel sockets) each with 20 OSDs and 4 SSDs (5 OSD 
journals on one SSD)
Client network: 10Gbps
Cluster network: 10Gbps
FIO test:
- 2 Client servers
- Sequential Read
- Run time of 600 seconds
- Filesize = 1TB
- 10 rbd images per client
- Queue depth=16

Any ideas on tuning this cluster?  Where should I look first?

Thanks,

- epk


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