[zfs-discuss] Re: Bottlenecking on CPU with SSDs, Tuning, Scheduling

Niels de Carpentier zfs at decarpentier.com
Tue Sep 10 16:11:44 EDT 2013


> On 09/10/2013 08:22 PM, Niels de Carpentier wrote:
>>> I'm seeing the same in an effort to get a pair of Fusion-io ioDrive2
>>> cards
>>> to work as mirrored pool devices. I'm not even getting 30% of the
>>> sequential throughput that I *should* be seeing.
>>
>> Are you using dedup as well?
>>
>> I could be that dedup is causing txg_sync load, as is causing an overal
>> slowdown.
>> It would be interesting to know if the same happens without dedup.
>
> If it is dedupe that is causing the insane txg_sync load and abismal
> performance (and that is a big if), considering that the recent
> Sandforce flash controllers dedupe the blocks anyway, and do so in
> realtime without any slowdown with a lot less CPU than a 3GHx Xeon, I'd
> like to hope that there are some vast improvements in ZFS planned WRT
> this particular feature.

While I don't disagree, I imagine it's a lot easier to do dedup with a
fixed number of fixed size blocks. And possibly the sandforce controllers
have hardware acceleration, or any do some kind of best effort dedup.

Niels
>
> Gordan
>
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