/usr/home vs /home

[Da Rock]

On 02/19/12 00:28, Matthew Seaman wrote:
> On 18/02/2012 13:48, Da Rock wrote:
>> I was thinking along the lines of continuous heavy load of writing (some
>> read) rather large files (5G+ would be average - multiple!) - does that
>> warrant caching or is it only lots of smaller files? That and lots of
>> ~0.5G files (read mostly) is what defines the main load on the system.
>>
>> I ask because I'm not 100% sure of what the caching is for. I had
>> thought it was like the journal log for fast writing to be later written
>> to the filesystem itself, but now I think I may be wrong in my
>> judgement. It now sounds like a fast access for usual suspects.
>>
>> Now you see how a terabyte and a half disk space can be used in a matter
>> of hours :)
> Right.  That's a lot more file IO than I anticipated in my previous
> answer.  For that amount of usage, 8GB would definitely be required and
> quite possibly more.  Separate devices for ZIL and ARC would be a good
> idea.  (ZIL is effectively the caching for the write path, ARC for the
> read path.  That's a gross over-simplification actually, but good enough.)
>
> The caching is vital -- it's where all the stuff like checking the
> parity for a RAIDZn device happens, or the compression/decompression
> actions.  Yes, it works like file system journalling too.
Thanks for the tips Matthew. Now you know why I haven't tackled that 
hurdle yet :)

I'm gunna need some serious hardware...