From: Jeff Wu <cpwu@tnsoft.com.cn>
To: "sage@newdream.net" <sage@newdream.net>, "ceph-devel@vger.kernel.org"
 <ceph-devel@vger.kernel.org>
Sender: "ceph-devel-owner@vger.kernel.org"
 <ceph-devel-owner@vger.kernel.org>
Date: Tue, 2 Nov 2010 14:49:58 +0800
Subject: Questions about ceph OSD
Thread-Topic: Questions about ceph OSD
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Hi ,

I have recently been working the preliminary research whether ceph 
can use at our cloud computing storage system in the future ,
ceph is a very very excellent file system.But ,Now ,i hit a very
important problem for us:

Normally, as ceph described , all of the data are saved at OSDs with
CRUSHMAP at ceph system.

but my goal is to :
1. add a ext3 disk to ceph system ,but doesn't set it as a OSD;
2. save the normal data at the OSDs of a ceph system;
3. save the special data to a local ext3 disk at a ceph system,
   the ext3 disk is not set as a ceph OSD,but its infos are added to 
  MDS and  MON,when Write the special data at a ceph client ,these
special data are not saved to ceph server OSDs ,but saved at the local
ext3 disk.

like this:
At ceph client:
$ mount.ceph 1.2.3.4:6789:/ /ceph
$ cd /ceph
$ ls
cloud user secret  

when do writing,"cloud and user" folder data are saved to ceph OSDs ,
but "secret" folder data are saved to a local ext3 disk .

My question is:
Q1- If i add a new OSD to the ceph system ,but i do a special CRUSH
placement map . Could this ways solved this problem ?,If can ,How ?

Q2 - If to implement this function as a patch myself, Could you give me
any ideas ? or what parts of ceph codes(server/client) that i need look
into ? 

Thanks for all help and reply .


Jeff.Wu
Transoft.inc ,Sr.software engineer.
　　

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