We actually use heap sizes from 32 to 64Gb for ours but our volumes and graphs 
are both extremely large. Although I believe the smaller heap sizes were a 
limitation of the garbage collection in Java 7. We also moved to ssd drives, 
which did help through put quite a bit. Our systems were actually requesting 
the creation and removal of file handles faster than traditional disks could 
keep up with (we believe). In addition, unlike with traditional drives where we 
tired to minimize caching, we actually forced more disk caching when we moved 
to ssds. Still waiting to see the results of that on our volumes, although it 
does seemed to have help. Also remember, depending on how you code them, 
individual processors can use system memory outside of the heap. So you need to 
take that into consideration when designing the servers. 

Sent from my iPhone

> On Oct 14, 2016, at 1:36 PM, Joe Witt <joe.w...@gmail.com> wrote:
> Russ,
> You can definitely find a lot of material on the Internet about Java heap 
> sizes, types of garbage collectors, application usage patterns.  By all means 
> please do experiment with different sizes appropriate for your case.  We're 
> not saying NiFi itself has any problem with large heaps.
> Thanks
> Joe
>> On Fri, Oct 14, 2016 at 12:44 PM, Russell Bateman 
>> <russell.bate...@perfectsearchcorp.com> wrote:
>> Ali,
>> "not recommended to dedicate more than 8-10 GM to JVM heap space" by whom? 
>> Do you have links/references establishing this? I couldn't find anyone 
>> saying this or why.
>> Russ
>>> On 10/13/2016 05:47 PM, Ali Nazemian wrote:
>>> Hi,
>>> I have another question regarding the hardware recommendation. As far as I 
>>> found out, Nifi uses on-heap memory currently, and it will not try to load 
>>> the whole object in memory. From the garbage collection perspective, it is 
>>> not recommended to dedicate more than 8-10 GB to JVM heap space. In this 
>>> case, may I say spending money on system memory is useless? Probably 16 GB 
>>> per each system is enough according to this architecture. Unless some 
>>> architecture changes appear in the future to use off-heap memory as well. 
>>> However, I found some articles about best practices, and in terms of memory 
>>> recommendation it does not make sense. Would you please clarify this part 
>>> for me?
>>> Thank you very much.
>>> Best regards,
>>> Ali
>>> On Thu, Oct 13, 2016 at 11:38 PM, Ali Nazemian <alinazem...@gmail.com> 
>>> wrote:
>>>> Thank you very much. 
>>>> I would be more than happy to provide some benchmark results after the 
>>>> implementation. 
>>>> Sincerely yours,
>>>> Ali
>>>>> On Thu, Oct 13, 2016 at 11:32 PM, Joe Witt <joe.w...@gmail.com> wrote:
>>>>> Ali,
>>>>> I agree with your assumption.  It would be great to test that out and 
>>>>> provide some numbers but intuitively I agree.
>>>>> I could envision certain scatter/gather data flows that could challenge 
>>>>> that sequential access assumption but honestly with how awesome disk 
>>>>> caching is in Linux these days in think practically speaking this is the 
>>>>> right way to think about it.
>>>>> Thanks
>>>>> Joe
>>>>> On Thu, Oct 13, 2016 at 8:29 AM, Ali Nazemian <alinazem...@gmail.com> 
>>>>> wrote:
>>>>>> Dear Joe,
>>>>>> Thank you very much. That was a really great explanation. 
>>>>>> I investigated the Nifi architecture, and it seems that most of the 
>>>>>> read/write operations for flow file repo and provenance repo are random. 
>>>>>> However, for content repo most of the read/write operations are 
>>>>>> sequential. Let's say cost does not matter. In this case, even choosing 
>>>>>> SSD for content repo can not provide huge performance gain instead of 
>>>>>> HDD. Am I right? Hence, it would be better to spend content repo SSD 
>>>>>> money on network infrastructure.
>>>>>> Best regards,
>>>>>> Ali
>>>>>>> On Thu, Oct 13, 2016 at 10:22 PM, Joe Witt <joe.w...@gmail.com> wrote:
>>>>>>> Ali,
>>>>>>> You have a lot of nice resources to work with there.  I'd recommend the 
>>>>>>> series of RAID-1 configuration personally provided you keep in mind 
>>>>>>> this means you can only lose a single disk for any one partition.  As 
>>>>>>> long as they're being monitored and would be quickly replaced this in 
>>>>>>> practice works well.  If there could be lapses in monitoring or time to 
>>>>>>> replace then it is perhaps safer to go with more redundancy or an 
>>>>>>> alternative RAID type.
>>>>>>> I'd say do the OS, app installs w/user and audit db stuff, application 
>>>>>>> logs on one physical RAID volume.  Have a dedicated physical volume for 
>>>>>>> the flow file repository.  It will not be able to use                   
>>>>>>>                             all the space but it certainly could 
>>>>>>> benefit from having no other contention.  This could be a great thing 
>>>>>>> to have SSDs for actually.  And for the remaining volumes split them up 
>>>>>>> for content and provenance as you have.  You get to make the overall 
>>>>>>> performance versus retention decision.                                  
>>>>>>>               Frankly, you have a great system to work with and I 
>>>>>>> suspect you're going to                                               
>>>>>>> see excellent results anyway.
>>>>>>> Conservatively speaking expect say 50MB/s of throughput per volume in 
>>>>>>> the content repository so if you end up with 8 of them could achieve 
>>>>>>> upwards of 400MB/s sustained.  You'll also then want to make sure you 
>>>>>>> have a good 10G based network setup as well.  Or, you could dial back 
>>>>>>> on the speed tradeoff and simply increase retention or disk loss 
>>>>>>> tolerance.  Lots of ways to play the game.
>>>>>>> There are no published SSD vs HDD performance benchmarks that I am 
>>>>>>> aware of though this is a good idea.  Having a hybrid of SSDs and HDDs 
>>>>>>> could offer a really solid performance/retention/cost tradeoff.  For 
>>>>>>> example having SSDs for the OS/logs/provenance/flowfile with HDDs for 
>>>>>>> the content - that would be quite nice.  At that rate to take full 
>>>>>>> advantage of the system you'd need to have very strong network 
>>>>>>> infrastructure between NiFi and any systems it is interfacing with  and 
>>>>>>> your flows would need to be well tuned for GC/memory efficiency.
>>>>>>> Thanks
>>>>>>> Joe 
>>>>>>> On Thu, Oct 13, 2016 at 2:50 AM, Ali Nazemian <alinazem...@gmail.com> 
>>>>>>> wrote:
>>>>>>>> Dear Nifi Users/ developers,
>>>>>>>> Hi,
>>>>>>>> I was wondering is there any benchmark about the question that is it 
>>>>>>>> better to dedicate disk control to Nifi                                
>>>>>>>>                          or using RAID for this purpose? For example, 
>>>>>>>> which of these scenarios is recommended from the performance point of 
>>>>>>>> view? 
>>>>>>>> Scenario 1: 
>>>>>>>> 24 disk in total
>>>>>>>> 2 disk- raid 1 for OS and fileflow repo
>>>>>>>> 2 disk- raid 1 for provenance repo1
>>>>>>>> 2 disk- raid 1 for provenance repo2
>>>>>>>> 2 disk- raid 1 for content repo1
>>>>>>>> 2 disk- raid 1 for content repo2
>>>>>>>> 2 disk- raid 1 for content repo3
>>>>>>>> 2 disk- raid 1 for content repo4
>>>>>>>> 2 disk- raid 1 for content repo5
>>>>>>>> 2 disk- raid 1 for content repo6
>>>>>>>> 2 disk- raid 1 for content repo7
>>>>>>>> 2 disk- raid 1 for content repo8
>>>>>>>> 2 disk- raid 1 for content repo9
>>>>>>>> Scenario 2: 
>>>>>>>> 24 disk in total
>>>>>>>> 2 disk- raid 1 for OS and fileflow repo
>>>>>>>> 4 disk- raid 10 for provenance repo1
>>>>>>>> 18 disk- raid 10 for content repo1
>>>>>>>> Moreover, is there any benchmark for SSD vs HDD performance for Nifi?
>>>>>>>> Thank you very much.
>>>>>>>> Best regards,
>>>>>>>> Ali
>>>>>> -- 
>>>>>> A.Nazemian
>>>> -- 
>>>> A.Nazemian
>>> -- 
>>> A.Nazemian

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