Re: re-export NFS mounted disk to be NFS mounted?

Yuri Csapo <ycsapo@xxxxxxxxx> · Mon, 23 Mar 2009 11:23:52 -0600

Well, a lot of it depends on the hardware you have, but re-exporting is 

really not a good idea no matter which protocol you use. Unless the 

cluster is a computational cluster which only needs to read/write disks 

sporadically, I'd strongly suggest you give it its own disk space, 

directly attached to the head node (or use a SAN, but that's beside the 

scope here I think).

We have a number of clusters here and there are 2 different solutions we 

use (that I'm aware of):

- For the big supercomputer we use a SAN which all nodes can see with 

Lustre as a filesystem. You can see hardware details here:

http://geco.mines.edu/hardware.shtml

- For small clusters (typically 10-node) we use disks directly attached 

to the head and NFS-exported to the nodes. This is just one hop of NFS 

so it's not that bad; still we work around it (after a fashion) by 

having local disks on each node that can be used as a temporary, 

node-specific scratch area.

Hope this helps...

Yuri

Yu Chen wrote:

Thanks Yuri,

Other than NFS, what else can I do, I heard a lot about NFS's 

performance, but I just don't know an alternative yet (AFP doesn't work 

that well on a server as what I read from mail lists, and from trying).

Guess I will go to local disk solution.

CY

On Mar 23, 2009, at 12:15 PM, Yuri Csapo wrote:

AFAIK that is not possible on Linux with the stock kernel nfs server. 

It *should*  be possible with the userspace server, but I'm not sure 

it's supported. Maybe someone who has actually done it (as opposed to 

playing with it) should comment.

OTOH it doesn't seem like a good idea anyway... NFS's performance is 

really bad and what you're doing will multiply bad x 2. I know 

sometimes you need to work with what you have but if your cluster is 

in any way I/O sensitive you should think about getting some local 

disk space for it, at least.

Yu Chen wrote:

Hello,

I have a cluster, the disk space is on a Xserver, it's NFS exported, 

and mounted on the cluster's head node without problem (mounted on 

/mnt/nfs), then I exported the "/mnt/nfs" directory, then tried to 

mount it on the nodes in the cluster (mount -t nfs headnode:/mnt/nfs 

/mnt/tmp), it gave error: mount ... failed, reason given by server: 

Permission denied.

my Xserver nfs exports entry has this: /Volumes/DataRAID  -alldirs 

-maproot=nobody -sec=sys -network my.headnode.network -mask 

255.255.255.0

my headnode mounted /Volumes/DataRAID on /mnt/nfs then exported as 

nfs exports entry:

/mnt/nfs 10.0.0.0/255.255.255.0(rw,sync)
Anybody has any suggestions?
Thanks in advance.
CY
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--
Yuri Csapo
Academic Computing & Networking
Colorado School of Mines
CT-256
Phone:  (303) 273-3503
Fax:      (303) 273-3475
Email:   ycsapo@xxxxxxxxx

Please use the following link to open a service request:
http://helpdesk.mines.edu
===========================================
With a PC, I always felt limited
by the software available.
On Unix, I am limited only by my knowledge.
--Peter J. Schoenster

--
Yuri Csapo
Academic Computing & Networking
Colorado School of Mines
CT-256
Phone:  (303) 273-3503
Fax:      (303) 273-3475
Email:   ycsapo@xxxxxxxxx

Please use the following link to open a service request:
http://helpdesk.mines.edu
===========================================
With a PC, I always felt limited
by the software available.
On Unix, I am limited only by my knowledge.
--Peter J. Schoenster
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