[9fans] Venti arenas and index guidelines

[9fans] Venti arenas and index guidelines

[Gregory Pavelcak]

Obviously I've had time on my hands to play with computers this week.

I have a fossil on an 18G hard drive, which from what I've seen, is
probably a much larger fossil than I need. However, I wasn't planning
on changing it unless it's really trivially easy to do so. I also have
another 18G drive and two 50G drives. I thought the thing to do would
be to mirror the 50G drives for venti arenas and that would leave the
18G drive for isects (and bloom?).

Any recommendations on how to proceed.

Thanks.

Greg

Re: [9fans] Venti arenas and index guidelines

[Russ Cox]

> I have a fossil on an 18G hard drive, which from what I've seen, is
> probably a much larger fossil than I need. However, I wasn't planning
> on changing it unless it's really trivially easy to do so. I also have
> another 18G drive and two 50G drives. I thought the thing to do would
> be to mirror the 50G drives for venti arenas and that would leave the
> 18G drive for isects (and bloom?).

Venti is much less sensitive to disk seek times than it once was.
(See http://swtch.com/~rsc/papers/fndn/ and s/Foundation/Venti/g.)
So to a first approximation, it basically doesn't matter what you do.

Mirroring is a good idea; that's a good argument for putting the
data on the 50G pair.  You could also put the isect and bloom filter
there, to keep the setup simple.  You only need 5% = 2.5G for
index; 18G is overkill.  The bloom filter helps most when you are
first initializing the venti, and for that it can be small (64MB is
probably plenty).

Russ