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Edward Ned Harvey wrote:
>> From: zfs-discuss-bounces@xxxxxxxxxxxxxxx [mailto:zfs-discuss-
>> bounces@xxxxxxxxxxxxxxx] On Behalf Of Arne Jansen
>>
>> There is absolutely no sense in having slog devices larger than
>> then main memory, because it will never be used, right?
>
> Also: A TXG is guaranteed to flush within 30 sec. Let's suppose you have a
> super fast device, which is able to log 8Gbit/sec (which is unrealistic).
> That's 1Gbyte/sec, unrealistically theoretically possible, at best. You do
> the math. ;-)
>
> That being said, it's difficult to buy an SSD smaller than 32G. So what are
> you going to do?
I'm still building my rotational write delay eliminating driver and am trying
to figure out how much space I can waste on the underlying device without ever
running into problems. I need half the physical memory, or, under the assumption
that it might be tunable, a maximum of my physical memory. It's good to know
a hard upper limit. The more I can waste, the faster the device will be.
Also, to stay in your line of argumentation, this super-fast slog is most
probably a DRAM-based, battery backed solution. In this case it will make
a difference if you buy 8 or 32GB ;)
--Arne
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