[Lustre-devel] flash cache page

[Peter J Braam]

>> 1 Use case table.
>>
>> i. we decided on an implementation constraint to store both file layouts 
>> as attributes of objects in a redirection layer in the client.  These 
>> layouts would be obtained from the MDS cluster, see (iv)
>>
>> ii. We decided that locks would be taken in a hierarchical  manner -  
>> the flash cache would run a LDLM and locks would be taken there.
>>
>> iii. Correctness would be handled automatically through the 
>> hierarchy.    
>>     
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>> However, to avoid a lot of reading "write only locks" used 
>> when entire pages are written are probably desirable (i.e. the caching 
>> infrastructure on the flash OST's is different from a Lustre client).
>>
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If a client writes a full page, the page should not first be read by the 
flash cache.  Almost too obvious perhaps.

- Peter -