Hi,
>>What I saw after enabling RBD cache it is working as expected, means sequential write has better MBps than random write. can somebody explain this behaviour ?
This is because rbd_cache merge coalesced ios in bigger ios, so it's working only with sequential workload.
you'll do less ios but bigger ios to ceph, so less cpus,....
----- Mail original -----
De: "Sumit Gaur" <sumitkgaur@xxxxxxxxx>
À: "Florent MONTHEL" <fmonthel@xxxxxxxxxxxxx>
Cc: "ceph-users" <ceph-users@xxxxxxxxxxxxxx>
Envoyé: Lundi 2 Février 2015 03:54:36
Objet: Re: ceph Performance random write is more then sequential
Hi All,
What I saw after enabling RBD cache it is working as expected, means sequential write has better MBps than random write. can somebody explain this behaviour ? Is RBD cache setting must for ceph cluster to behave normally ?
Thanks
sumit
On Mon, Feb 2, 2015 at 9:59 AM, Sumit Gaur < sumitkgaur@xxxxxxxxx > wrote:
Hi Florent,
Cache tiering , No .
** Our Architecture :
vdbench/FIO inside VM <--> RBD without cache <-> Ceph Cluster (6 OSDs + 3 Mons)
Thanks
sumit
[root@ceph-mon01 ~]# ceph -s
cluster 47b3b559-f93c-4259-a6fb-97b00d87c55a
health HEALTH_WARN clock skew detected on mon.ceph-mon02, mon.ceph-mon03
monmap e1: 3 mons at {ceph-mon01= 192.168.10.19:6789/0,ceph-mon02=192.168.10.20:6789/0,ceph-mon03=192.168.10.21:6789/0 }, election epoch 14, quorum 0,1,2 ceph-mon01,ceph-mon02,ceph-mon03
osdmap e603: 36 osds: 36 up, 36 in
pgmap v40812: 5120 pgs, 2 pools, 179 GB data, 569 kobjects
522 GB used, 9349 GB / 9872 GB avail
5120 active+clean
On Mon, Feb 2, 2015 at 12:21 AM, Florent MONTHEL < fmonthel@xxxxxxxxxxxxx > wrote:
BQ_BEGIN
Hi Sumit
Do you have cache pool tiering activated ?
Some feed-back regarding your architecture ?
Thanks
Sent from my iPad
> On 1 févr. 2015, at 15:50, Sumit Gaur < sumitkgaur@xxxxxxxxx > wrote:
>
> Hi
> I have installed 6 node ceph cluster and to my surprise when I ran rados bench I saw that random write has more performance number then sequential write. This is opposite to normal disk write. Can some body let me know if I am missing any ceph Architecture point here ?
> _______________________________________________
> ceph-users mailing list
> ceph-users@xxxxxxxxxxxxxx
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
BQ_END
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