[Gluster-users] Caching differences in Gluster vs Local Storage

[Jeremy Enos]

I'll second that question.  Is there a way to get Gluster to see the 
same cache benefit that direct filesystem or NFS enjoys?

     Jeremy

On 4/2/2010 2:38 AM, Jon Swanson wrote:
> Yeah, obviously it's not actually writing to physical disks. I'm 
> assuming that because it's a small file size (32GB), most of that is 
> just hitting the filesystem cache.
>
> What i'm curious about is why Gluster is not seeing similar benefits 
> from filesystem cache.
>
> It is getting /some/ benefit:
> [root at linuxdb1 tiobench-gluster.2]# tiotest -b 16384 -r 4096 -f 32 -t 
> 16 -d .
> Tiotest results for 16 concurrent io threads:
> ,----------------------------------------------------------------------.
> | Item                  | Time     | Rate         | Usr CPU  | Sys CPU |
> +-----------------------+----------+--------------+----------+---------+
> | Write         512 MBs |   16.7 s |  30.731 MB/s |   2.0 %  |  33.5 % |
> | Random Write 1024 MBs |   38.9 s |  26.314 MB/s |   1.8 %  |  32.5 % |
> | Read          512 MBs |    4.8 s | 107.145 MB/s |   4.0 %  | 221.4 % |
> | Random Read  1024 MBs |    4.2 s | 241.220 MB/s |  11.6 %  | 543.4 % |
>
> There's no way it's getting 241 MB/s over gigabit with Random Read. 
> I'm sure there's a reason for this, just curious as to what it is.
>
> On 04/02/2010 04:29 PM, Marcus Bointon wrote:
>> On 2 Apr 2010, at 09:10, Jon Swanson wrote:
>>
>>> ,----------------------------------------------------------------------. 
>>>
>>> | Item                  | Time     | Rate         | Usr CPU  | Sys 
>>> CPU |
>>> +-----------------------+----------+--------------+----------+---------+ 
>>>
>>> | Write         512 MBs |   35.7 s |  14.361 MB/s |   0.5 %  | 833.8 
>>> % |
>>> | Random Write 1024 MBs |  100.6 s |  10.182 MB/s |   0.4 %  | 379.5 
>>> % |
>>> | Read          512 MBs |    0.1 s | 4043.978 MB/s |  74.2 %  | 
>>> 5832.1 % |
>>> | Random Read  1024 MBs |    0.2 s | 4171.521 MB/s | 131.2 %  | 
>>> 6425.0 % |
>>> `----------------------------------------------------------------------' 
>>>
>> Either these numbers or units are wrong or you have some outrageously 
>> fast disks! 4Gbytes/sec?? You have multiple FusionIOs or something?
>>
>> Marcus
>
>
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