The Overlooked Cache . . .

Xsan Cows,

I bought an additional XserveRAID on where else . . . eBay that I'm getting around to fully configuring. I just noticed though that it only has a measly 128MB cache per controller instead of the desired 512 which my other RAID's have. How will this effect my work and should I immediately upgrade the cache (probably). I can't remember what this cache is actually used for, I only remember that it ought to be 512 per side. Can anyone enlighten me? And what pray tell will this small upgrade cost?

Thanks for the info.

David