Performance Difference on UFS and ZFS

[Metin Döşlü]

Hi Sergey,

I tested it on a cc1.4xlarge EC2 instance, here is the specs:

23 GiB of memory
33.5 EC2 Compute Units (2 x Intel Xeon X5570, quad-core “Nehalem” architecture)
1690 GB of instance storage
64-bit platform

I installed PostgreSQL from its port on FreeBSD. I didn't do any
tuning for PostgreSQL or FreeBSD. Data access pattern consists of
completely from sequential reads such "select count(*) from
table_name". I measured performance with PostgreSQL's timing option.
As as side note; all queries are served from memory, so there were no
disk usage for these tests.

Thanks,
Metin

On Wed, Nov 28, 2012 at 4:49 PM, Sergey Kandaurov <pluknet at gmail.com> wrote:
> On 28 November 2012 12:35, Metin Döşlü <metindoslu at gmail.com> wrote:
>> Hi -
>>
>> I installed PostgreSQL 9.1.6 on FreeBSD 9.0-RELEASE, and compared ZFS
>> to UFS. I also made sure all data easily fit into memory, ran some
>> sequential scan queries on the database.
>>
>> Query run times on UFS were 100-200% slower than those of ZFS. This
>> was intriguing as all data came from memory. What could be causing
>> such a large performance difference?
>
> Hi Metin Döşlü!
>
> That's interesting. Can you please share your settings?
> Hardware configuration, system tuning (sysctl, zfs), PostgreSQL settings,
> data access pattern (read/write ratio), and how you measure performance
> would be a good start.
>
> --
> wbr,
> pluknet



-- 
Metin Döşlü