[Gluster-devel] Scaled down a bit.

Chris Johnson johnson at nmr.mgh.harvard.edu
Thu Nov 29 14:10:32 UTC 2007

On Wed, 28 Nov 2007, Anand Babu Periasamy wrote:

      MRI imaging.  The real programs suck in between 5 and 8 MB worth
of image, crunch them for what seems forever, and then write the
resulting image.  They do this for about 100 slices per scan.  We have a
300 node cluster that runs these things.  This means the local private
gigbit net they're on and the servers are periodically swamped to say
the least.  Not a lot of client rereading going on and I discovered
the caching on the server didn't really help yesterday.  I tried
readahead and that was statistically zero help, pages wre 2 and page
size was 128KB.  I tried a 512KB page size and for some reason made
matters worse apparently.

      Based on whats below I think io-threads might help in the
multi-node case.

      Any help appreciated.

> io-thread on client side improves performance when multiple files are 
> read/written simultaneously by multiple applications or a single 
> muli-threaded application.
> In terms of few ms difference between nfs and glusterfs, there are some
> more performance optimizations possible. Booster will also help you.
> We balance between elegance and performance. Our focus was on scalability and 
> reliability so far. It made sense for us to take advantage of
> modern technologies like Infiniband/10GigE RDMA, Clustered I/O, high
> level performance modules to show several times more performance than
> NFS instead of worrying about little issues. Avati is just testing new
> patch that will put fuse on separate thread on client side. This will improve 
> responsiveness :)
> If you tell us more about your application environment, we can suggest
> if there are ways to improve performance further.
> Chris Johnson writes:
>> On Wed, 28 Nov 2007, Kevan Benson wrote:
>>       Ok, better.  Does work on the client side though.  Doesn't seem
>> to be to great on the server side for some reason.
>>       I just tried my simple test with readahead on the cl;ient side.
>> No difference.  Here's what I used.
>> volume readahead
>>    type performance/read-ahead
>>    option page-size 128kb ### in bytes
>>    option page-count 2 ### memory cache size is page-count x page-size per 
>> file
>>    subvolumes client
>> end-volume
>> ~ Maybe the page size or count needs to be bigger?
>>> Krishna Srinivas wrote:
>>>> On Nov 28, 2007 11:11 PM, Chris Johnson <johnson at nmr.mgh.harvard.edu> 
>>>> wrote:
>>>>> On Wed, 28 Nov 2007, Kevan Benson wrote:
>>>>>> Chris Johnson wrote:
>>>>>>>      I also tried the io-cache on the client side.  MAN does that
>>>>>>> work.  I had a 256 MB cache defind.  A reread of my 24 MB file took 72
>>>>>>> MS.  I don't think it even bothered with the server much.  I need to
>>>>>>> try that on the server.  Might help if a bunch of computer nodes
>>>>>>> hammer on the same file at the same time.
>>>>>> Careful with io-cache and io-threads together, depending on where you 
>>>>>> define
>>>>>> it (I think), the cache is per-thread.  so if you have 8 threads and a 
>>>>>> 256 MB
>>>>>> cache defined, be prepared for 2 GB of cache use...
>>>> No, If you define one io-cache translator there is only one cache. All 
>>>> the
>>>> threads will refer to the same io-cache translator with which it is 
>>>> associated
>>> Ah.  Is this newer?  I thought I tried this a few months ago and saw a lot 
>>> of memory usage.  Maybe I just ASSumed. ;)
>>> -- 
>>> -Kevan Benson
>>> -A-1 Networks
>> ------------------------------------------------------------------------------- 
>> Chris Johnson               |Internet: johnson at nmr.mgh.harvard.edu
>> Systems Administrator       |Web: 
>> http://www.nmr.mgh.harvard.edu/~johnson
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> -- 
> Anand Babu Periasamy
> GPG Key ID: 0x62E15A31
> Blog [http://ab.freeshell.org]
> The GNU Operating System [http://www.gnu.org]

Chris Johnson               |Internet: johnson at nmr.mgh.harvard.edu
Systems Administrator       |Web:      http://www.nmr.mgh.harvard.edu/~johnson
NMR Center                  |Voice:    617.726.0949
Mass. General Hospital      |FAX:      617.726.7422
149 (2301) 13th Street      |"Survival is insufficient"
Charlestown, MA., 02129 USA |             Seven of nine.

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