Overhead of Using a Stackable File System(Wrapfs)

Overhead of Using a Stackable File System(Wrapfs)

[UZAIR LAKHANI]

Hello All,

I want to enquire about the percent overhead involved
when we use Wrapfs(null layer stacking file system)
over ext3.

I want to enquire this because I want to use Wrapfs in
a network environment and there will be an additional
overhead of network communication.

Thanks,
Uzair Lakhani,
Karachi, Pakistan.

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Re: Overhead of Using a Stackable File System(Wrapfs)

[Avishay Traeger]

On Sun, 2006-04-02 at 01:32 -0800, UZAIR LAKHANI wrote:
> Hello All,
> 
> I want to enquire about the percent overhead involved
> when we use Wrapfs(null layer stacking file system)
> over ext3.

It should only be a few percent (if I remember correctly, less than 5),
but it would depend on your machine and workload.  If you want an exact
answer, just run some benchmarks on ext3 and wrapfs/ext3.

> I want to enquire this because I want to use Wrapfs in
> a network environment and there will be an additional
> overhead of network communication.

If you're still talking about implementing NFS using stackable file
systems, please note that we decided that was not a good idea.

Good luck.

Avishay Traeger
http://www.fsl.cs.sunysb.edu/~avishay/

Re: Overhead of Using a Stackable File System(Wrapfs)

[UZAIR LAKHANI]

--- Avishay Traeger <atraeger@cs.sunysb.edu> wrote:

> On Sun, 2006-04-02 at 01:32 -0800, UZAIR LAKHANI
> wrote:
> > Hello All,
> > 
> > I want to enquire about the percent overhead
> involved
> > when we use Wrapfs(null layer stacking file
> system)
> > over ext3.
> 
> It should only be a few percent (if I remember
> correctly, less than 5),
> but it would depend on your machine and workload. 
> If you want an exact
> answer, just run some benchmarks on ext3 and
> wrapfs/ext3.
> 
> > I want to enquire this because I want to use
> Wrapfs in
> > a network environment and there will be an
> additional
> > overhead of network communication.
> 
> If you're still talking about implementing NFS using
> stackable file
> systems, please note that we decided that was not a
> good idea.

Thanks for replying but consider this scenario.

What Wrapfs code do is this 

user_request ---> vfs_request ---> wrapfs_request --->
actual_fs_request ---> storage

Now consider this scenario in a network environment

(client machine)
user_request ---> vfs_request ---> wrapfs_request --->

Network ---> (server machine)actual_fs_request --->
storage

The network here gets client requests and send them to
server and vice versa.


> 
> Good luck.
> 
> Avishay Traeger
> http://www.fsl.cs.sunysb.edu/~avishay/
> 
> 


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Re: Overhead of Using a Stackable File System(Wrapfs)

[Avishay Traeger]

On Fri, 2006-04-07 at 23:48 -0700, UZAIR LAKHANI wrote:
> Thanks for replying but consider this scenario.
> 
> What Wrapfs code do is this 
> 
> user_request ---> vfs_request ---> wrapfs_request --->
> actual_fs_request ---> storage
> 
> Now consider this scenario in a network environment
> 
> (client machine)
> user_request ---> vfs_request ---> wrapfs_request --->
> 
> Network ---> (server machine)actual_fs_request --->
> storage
> 
> The network here gets client requests and send them to
> server and vice versa.

The main benefit of stackable file systems is that you do not need to
duplicate the functionality found in lower-level file systems.  In your
scenario, you do not use the lower-level file system at all, so you will
need to implement all the functionality of a lower-level file system,
plus deal with all the stackable file system code (which you will use
but won't need).  Using wrapfs in this case will give you no benefit,
and will just make your life more difficult, and your code slower and
more difficult to read.  I recommend you just start from scratch.

Avishay Traeger
http://www.fsl.cs.sunysb.edu/~avishay/

Re: Overhead of Using a Stackable File System(Wrapfs)

[UZAIR LAKHANI]

--- Avishay Traeger <atraeger@cs.sunysb.edu> wrote:

> On Fri, 2006-04-07 at 23:48 -0700, UZAIR LAKHANI
> wrote:
> > Thanks for replying but consider this scenario.
> > 
> > What Wrapfs code do is this 
> > 
> > user_request ---> vfs_request ---> wrapfs_request
> --->
> > actual_fs_request ---> storage
> > 
> > Now consider this scenario in a network
> environment
> > 
> > (client machine)
> > user_request ---> vfs_request ---> wrapfs_request
> --->
> > 
> > Network ---> (server machine)actual_fs_request
> --->
> > storage
> > 
> > The network here gets client requests and send
> them to
> > server and vice versa.
> 
> The main benefit of stackable file systems is that
> you do not need to
> duplicate the functionality found in lower-level
> file systems.  In your
> scenario, you do not use the lower-level file system
> at all, so you will
> need to implement all the functionality of a
> lower-level file system,
> plus deal with all the stackable file system code
> (which you will use
> but won't need).  Using wrapfs in this case will
> give you no benefit,
> and will just make your life more difficult, and
> your code slower and
> more difficult to read.  I recommend you just start
> from scratch.
> 
Thanks again for replying. I am getting your point
that we don't have any lower filesystem on the client
side but can we not assume that we have a lower file
sytem on client side but that actually resides across
the network on server side. All then we have to do is
to pass the requsts for the lower file system on
client side to the lower file system on server side
using some communication mechanism.

Waiting for comments.

Thanks,
Uzair

> Avishay Traeger
> http://www.fsl.cs.sunysb.edu/~avishay/
> 
> 


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Re: Overhead of Using a Stackable File System(Wrapfs)

[Erez Zadok]

You can find a lot of papers spanning several years and covering a wide
variety of stackable file systems, with detailed performance evaluations,
here:

	http://www.filesystems.org/

Erez.