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Re: With 4 disks should I go for RAID 5 or RAID 10

From: Shane Ambler <pgsql(at)Sheeky(dot)Biz>
To: Mark Mielke <mark(at)mark(dot)mielke(dot)cc>
Cc: Fernando Hevia <fhevia(at)ip-tel(dot)com(dot)ar>, 'pgsql-performance' <pgsql-performance(at)postgresql(dot)org>
Subject: Re: With 4 disks should I go for RAID 5 or RAID 10
Date: 2007-12-27 07:16:38
Message-ID: 47735156.2080403@Sheeky.Biz (view raw or flat)
Thread:
Lists: pgsql-performance
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

Get Sheeky @ http://Sheeky.Biz

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Next:From: Shane AmblerDate: 2007-12-27 07:39:51
Subject: Re: With 4 disks should I go for RAID 5 or RAID 10
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Subject: Re: More shared buffers causes lower performances

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