hi Masters:
      i want to develop a log structure filesystem based on hdfs。this 
filesystem used to host virtualizaion machine image file 。
      on hdfs i can implement snapshot and data redundancy;as log structure fs 
,which support random access。
i also hope to use map reduce way to do segment cleaning partly。
     i am not sure if it is reasonable 。i really hope to build a env that 
support online app and offline app at same time。i am trying do it on hdfs。can 
you give me some advice?
 thanks
kanghua
发自我的 iPhone

在 2011-9-15,14:54,Norman Maurer <norman.mau...@googlemail.com> 写道:

> You should keep in mind that HDFS is not POSIX conform so you will
> have a hard time to use it as "real fs". I know there is a fuse driver
> for it but I would not use it for heavy usage. Also HDFS is not really
> a good fit for random access at all.
> 
> If you really need a POSIX fs I would recomment you to have a look at
> DRBD or glusterfs..
> 
> Bye,
> Norman
> 
> 
> 2011/9/15 Per Steffensen <st...@designware.dk>:
>> David Rosenstrauch skrev:
>>> 
>>> On 09/14/2011 02:02 PM, Per Steffensen wrote:
>>>> 
>>>> Hi
>>>> 
>>>> If my goal is to have multiple physical disks seem as one big disk with
>>>> redundancy built in, why would I use a HDFS cluster among machines with
>>>> one disk each, instead of using software RAID like md(adm) directly on
>>>> top of the disks? I am looking for pros and cons on the two solutions.
>>>> http://en.wikipedia.org/wiki/RAID#Software-based_RAID
>>>> http://en.wikipedia.org/wiki/Mdadm
>>>> 
>>>> Regards, Per Steffensen
>>> 
>>> HDFS was never intended to be a general-purpose file system.  It is a
>>> system optimized for a) running map/reduce, and b) holding large files.  It
>>> should not be considered as a replacement for RAID.
>>> 
>>> DR
>> 
>> Thanks for you reply, David. Despite that HDFS wasnt intended to be used for
>> this, I guess it could be. So if we forget for a moment that it was not
>> designed/optimized to be used as a general purpose file system (GPFS), what
>> are the pros and cons for using it as a GPFS with built in redundancy vs
>> using software RAID. Is HDFS too slow for some kind of file operations, or
>> what will the problems (and benefits) be? Hope for some input - I need
>> arguments for and against to be used in a discussion with a customer.
>> Thanks!
>>> 
>>> 
>> 
>> 
> 

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