[Lustre-devel] LustreFS performance

[Jeff Darcy]

Oleg Drokin wrote:
> On Mar 2, 2009, at 3:45 PM, Andreas Dilger wrote:
>
>   
>> On Mar 02, 2009  20:04 +0300, Vitaly Fertman wrote:
>>     
>>>   RAM: enough to have a tmpfs for MDS;
>>>       
>> Note that strictly speaking we need to use ldiskfs on a ramdisk, not
>> tmpfs, because we don't have an fsfilt_tmpfs.
>>     
>
> The idea was loop device on tmpfs, I think.
>   

FYI, this is exactly what we do with our FabriCache feature - i.e. both 
MDT and OSTs are actually loopback files on tmpfs.  Modulo a few issues 
with preallocated write space eating all storage leaving none for actual 
data, it works rather well producing high performance numbers and giving 
LNDs a good workout.  BTW, the loopback driver does copies and is 
disturbingly single-threaded, which can create a bottleneck.  This can 
be worked around with multiple instances per node, though.