Subject: Re: [vserver] HASH FS
From: John Francis Lee <jfl@robinlea.com>
Date: Sat, 26 Jul 2008 05:12:25 +0700

Jun OKAJIMA wrote:
>>  Can you compare and contrast your work with the Venti file system from
>>  plan9? I believe that it too is a hash-based, write-once, immutable
>>  filesystem, isn't it? Or do I misunderstand what you, and they, have done?
>>
>>
> 
> You are right.
> Venti and HASH FS have common stuff.
> They use hash to share same data.
> 
> The biggest difference is,
> Venti is used for keeping your own data,
> but HASH FS is for existent data.
> And, "existent data" is, in short, ready-made disk images for virtual server.
> 
> Venti can share same sector between VEs,
> but you have to install all files before
> you use VE, and you dont have to delete files.
> In HASH FS, you dont need any blob installed
> before you use.
> Blobs are fetched on demand,
> and you can delete them any time.
> 
> Another merit of HASH FS is,
> it is faster, theoretically.
> 
> So, if you want to share your own data (like logs)
> between VEs, Venti would be a choice,
> but you want to share ready-made files (.deb/.rpm),
> HASH FS is better.
> 
>       --- Okajima, Jun. Tokyo, Japan.
>             http://www.machboot.com/
>             http://www.digitalinfra.co.jp/
> 
Thank you very much for the elaboration.

-- 
John Francis Lee
1025/37 Thanon Jet Yawt
T.Wiang A.Mueang J.Chiangrai 57000