Message-ID: <47735156.2080403@Sheeky.Biz>
Date: Thu, 27 Dec 2007 17:46:38 +1030
From: Shane Ambler <pgsql@Sheeky.Biz>
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To: Mark Mielke <mark@mark.mielke.cc>
CC: Fernando Hevia <fhevia@ip-tel.com.ar>,
	'pgsql-performance' <pgsql-performance@postgresql.org>
Subject: Re: With 4 disks should I go for RAID 5 or RAID 10
References: <0f9701c84801$399dcff0$8f01010a@iptel.com.ar>
	<47731D32.3040403@Sheeky.Biz> <47732BCB.2090302@mark.mielke.cc>
In-Reply-To: <47732BCB.2090302@mark.mielke.cc>
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Mark Mielke wrote:
> Shane Ambler wrote:
>> So in a perfect setup (probably 1+0) 4x 300MB/s SATA drives could
>> deliver 1200MB/s of data to RAM, which is also assuming that all 4
>> channels have their own data path to RAM and aren't sharing. 
>> (anyone know how segregated the on board controllers such as these
>> are?)
 >> (do some pci controllers offer better throughput?)
 >> We all know that doesn't happen in the real world ;-) Let's say we
 >> are restricted to 80% - 1000MB/s - and some of that (10%) gets used
 >> by the system - so we end up with 900MB/s delivered off disk to
>> postgres - that would still be more than the perfect rate at which
>> 2x 300MB/s drives can deliver.
> 
> I achieve something closer to +20% - +60% over the theoretical 
> performance of a single disk with my four disk RAID 1+0 partitions.

If a good 4 disk SATA RAID 1+0 can achieve 60% more throughput than a 
single SATA disk, what sort of percentage can be achieved from a good 
SCSI controller with 4 disks in RAID 1+0?

Are we still hitting the bus limits at this point or can a SCSI RAID 
still outperform in raw data throughput?

I would still think that SCSI would still provide the better reliability 
that it always has, but performance wise is it still in front of SATA?


-- 

Shane Ambler
pgSQL (at) Sheeky (dot) Biz

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