On 09/26/2012 01:14 PM, Edward Ned Harvey
(opensolarisisdeadlongliveopensolaris) wrote:
>> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
>> boun...@opensolaris.org] On Behalf Of Jim Klimov
>>
>> Got me wondering: how many reads of a block from spinning rust
>> suffice for it to ultimately get into L2ARC? Just one so it
>> gets into a recent-read list of the ARC and then expires into
>> L2ARC when ARC RAM is more needed for something else,
>
> Correct, but not always sufficient. I forget the name of the parameter, but
> there's some rate limiting thing that limits how fast you can fill the L2ARC.
> This means sometimes, things will expire from ARC, and simply get discarded.
The parameters are:
*) l2arc_write_max (default 8MB): max number of bytes written per
fill cycle
*) l2arc_headroom (default 2x): multiplies the above parameter and
determines how far into the ARC lists we will search for buffers
eligible for writing to L2ARC.
*) l2arc_feed_secs (default 1s): regular interval between fill cycles
*) l2arc_feed_min_ms (default 200ms): minimum interval between fill
cycles
Cheers,
--
Saso
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