LOL, I actually was unclear not you.  I understood what you were saying,
sorry for being unclear.  I have 4 disks in raid10, so my max random read
throughput is theoretically somewhat faster than the L2ARC device, but I
never really do that intensive of reads.  My point was: if a guest does read
a bunch of data sequentially, that will trigger the prefetch L2ARC code
path, correct?  If so, I *do* want that cache in L2ARC, so that a return
visit from that guest will hit as much as possible in the cache.  One other
thing (I don't think I mentioned this): my entire ESXi dataset is only like
160GB (thin provisioning in action), so it seems to me, I should be able to
fit the entire thing in L2ARC? 

-----Original Message-----
From: Sašo Kiselkov [] 
Sent: Tuesday, September 11, 2012 9:35 AM
To: Dan Swartzendruber
Cc: 'James H';
Subject: Re: [zfs-discuss] Interesting question about L2ARC

On 09/11/2012 03:32 PM, Dan Swartzendruber wrote:
> I think you may have a point.  I'm also inclined to enable prefetch 
> caching per Saso's comment, since I don't have massive throughput - 
> latency is more important to me.

I meant to say the exact opposite: enable prefetch caching only if your
l2arc is faster (in terms of bulk throughput) than your disks. Prefetch
isn't latency bound by its very definition, so it generally makes little
reason to l2arc cache it.


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