Message-ID: <4E4C10C9.1000806@gpdnet.co.uk>
Date: Wed, 17 Aug 2011 20:04:41 +0100
From: Gary Doades <gpd@gpdnet.co.uk>
User-Agent: Mozilla/5.0 (Windows NT 6.1;
 rv:6.0) Gecko/20110812 Thunderbird/6.0
MIME-Version: 1.0
To: Ogden <lists@darkstatic.com>
CC: pgsql-performance@postgresql.org
Subject: Re: Raid 5 vs Raid 10 Benchmarks Using bonnie++
References: <959BD2FA-0312-458B-BD5F-ED358D2C47ED@darkstatic.com>
	<f4e06a7cad34ee9217a3e57fd4eb0e67.squirrel@sq.gransy.com>
	<D89151D3-D2E5-47E3-8B90-4A573DAB5FFA@darkstatic.com>
	<75A85649-2B95-43D5-8404-4776D2E580EC@darkstatic.com>
	<4E4C0969.5030401@gpdnet.co.uk>
	<AE7D7AD5-0948-438E-BA75-E12A8EB44446@darkstatic.com>
In-Reply-To: <AE7D7AD5-0948-438E-BA75-E12A8EB44446@darkstatic.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

On 17/08/2011 7:56 PM, Ogden wrote:
> On Aug 17, 2011, at 1:33 PM, Gary Doades wrote:
>
>> On 17/08/2011 7:26 PM, Ogden wrote:
>>> I am using bonnie++ to benchmark our current Postgres system (on RAID 5) with the new one we have, which I have configured with RAID 10. The drives are the same (SAS 15K). I tried the new system with ext3 and then XFS but the results seem really outrageous as compared to the current system, or am I reading things wrong?
>>>
>>> The benchmark results are here:
>>>
>>> http://malekkoheavyindustry.com/benchmark.html
>>>
>> The results are not completely outrageous, however you don't say what drives, how many and what RAID controller you have in the current and new systems. You might expect that performance from 10/12 disks in RAID 10 with a good controller. I would say that your current system is outrageous in that is is so slow!
>>
>> Cheers,
>> Gary.
>
> Yes, under heavy writes the load would shoot right up which is what caused us to look at upgrading. If it is the RAID 5, it is mind boggling that it could be that much of a difference. I expected a difference, now that much.
>
> The new system has 6 drives, 300Gb 15K SAS and I've put them into a RAID 10 configuration. The current system is ext3 with RAID 5 over 4 disks on a Perc/5i controller which has half the write cache as the new one (256 Mb vs 512Mb).
Hmm... for only 6 disks in RAID 10 I would say that the figures are a 
bit higher than I would expect. The PERC 5 controller is pretty poor in 
my opinion, PERC 6 a lot better and the new H700's pretty good. I'm 
guessing you have a H700 in your new system.

I've just got a Dell 515 with a H700 and 8 SAS in RAID 10 and I only get 
around 600 MB/s read using ext4 and Ubuntu 10.4 server.

Like I say, your figures are not outrageous, just unexpectedly good :)

Cheers,
Gary.