On Mon, Feb 7, 2011 at 1:06 PM, Brandon High <bh...@freaks.com> wrote:
> On Mon, Feb 7, 2011 at 6:15 AM, Yi Zhang <yizhan...@gmail.com> wrote:
>> On Mon, Feb 7, 2011 at 12:25 AM, Richard Elling
>> <richard.ell...@gmail.com> wrote:
>>> Solaris UFS directio has three functions:
>>> 1. improved async code path
>>> 2. multiple concurrent writers
>>> 3. no buffering
>>>
>> Thanks for the comments, Richard. All I wanted is to achieve 3 on ZFS.
>> But as I said, apprently 2.a) below didn't give me that. Do you have
>> any suggestion?
>
> Don't. Use a ZIL, which will meet the requirements for synchronous IO.
> Set primarycache to metadata to prevent caching reads.
>
> ZFS is a very different beast than UFS and doesn't require the same tuning.
>
I already set primarycache to metadata, and I'm not concerned about
caching reads, but caching writes. It appears writes are indeed cached
judging from the time of 2.a) compared to UFS+directio. More
specifically, 80MB/2s=40MB/s (UFS+directio) looks realistic while
80MB/0.11s=800MB/s (ZFS+primarycache=metadata) doesn't.
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