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Testing Log-Write-Cache

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Testing Log-Write-Cache

Postby Arcyne » Fri Dec 28, 2018 2:26 am

Hello all,

Testing Environment:
Mixed Pool of HDD and SSD's.

I've been testing the Log-Write-Cache feature and so far I really like it for its benefits on write performance. That said, I'm looking to combine that functionality with the ability to also have a dedicated L2-Read cache. Right now, during the Log-Write-Cache does seem to support reads while the cache logs are present but after the write-cache-logs are persisted to HDD tier they are removed and so all future reads are read directly from the HDD tier.

So my questions are:

1.) Is this the expected behavior? (e.g. should the write-cache-logs flush)
2.) If the log flush is expected (likely as you would want it to..) Is there the possibility of also defining a L2 write-through cache so that we can also get read-caching.

Note: I've messed around with a throwaway environment and attempting to add-level-2-cache FAQ entries but so far no go.... It could be a mistake on my part but I'm also pretty sure that I'm off of the range so to speak.

Thanks All,
Ryan
Arcyne
 
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Re: Testing Log-Write-Cache

Postby Arcyne » Wed Jan 02, 2019 5:06 pm

Ping? Bringing back to top after holiday break... :-)
Arcyne
 
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Re: Testing Log-Write-Cache

Postby Arcyne » Thu Jan 03, 2019 9:02 pm

Hmm, crickets? Staff, could you respond even if it is no comment?
Arcyne
 
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Re: Testing Log-Write-Cache

Postby Oleg(staff) » Fri Jan 04, 2019 5:50 pm

Hello Archine,
1.) Is this the expected behavior? (e.g. should the write-cache-logs flush)

LWC is the device that boosts up write operations with the help of an additional layer of storage. It is not recommended to use this layer for reads, it can cause performance issues because of LWC nature(data can be divided to several parts). The main task of LWC is to move data to the backend before the client will need this data. Read/write work is separated between two storages with this scenario. LWC boosts up the reads only because of work separation between two layers of device and data load optimization during the process of migration to the backend and the frontend is not intended for a long period data caching.

2.) If the log flush is expected (likely as you would want it to..) Is there the possibility of also defining a L2 write-through cache so that we can also get read-caching.


Yes, for reads boost up you need Write-Though caching. The scenario with L2 caching will be added for sure. But for this test version it is not added and not tested yet.
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Re: Testing Log-Write-Cache

Postby Arcyne » Fri Jan 04, 2019 9:06 pm

Perfect! Thanks for the clarification. :-)
If you need an alpha tester let me know.
Arcyne
 
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Re: Testing Log-Write-Cache

Postby Oleg(staff) » Sat Jan 05, 2019 8:21 am

You are welcome :)
Sure :wink:
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