Re: suggestions for postgresql setup on Dell 2950 , PERC6i controller

From: Ivan Voras <ivoras(at)freebsd(dot)org>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: suggestions for postgresql setup on Dell 2950 , PERC6i controller
Date: 2009-02-05 13:01:07
Message-ID: gmenup$1ca$1@ger.gmane.org
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Matt Burke wrote:
> Arjen van der Meijden wrote:
>
>> Afaik the Perc 5/i and /e are more or less rebranded LSI-cards (they're
>> not identical in layout etc), so it would be a bit weird if they
>> performed much less than the similar LSI's wouldn't you think?
>
> I've recently had to replace a PERC4/DC with the exact same card made by
> LSI (320-2) because the PERCs firmware was crippled. Its idea of RAID10
> actually appears to be concatenated RAID1 arrays.
>
> Since replacing it and rebuilding the array on the LSI card, performance
> has been considerably better (14 disk SCSI shelf)
>
>> Areca may be the fastest around right now, but if you'd like to get it
>> all from one supplier, its not too bad to be stuck with Dell's perc 5 or
>> 6 series.
>
> The PERC6 isn't too bad, however it grinds to a halt when the IO queue
> gets large and it has the serious limitation of not supporting more than
> 8 spans, so trying to build a RAID10 array greater than 16 disks is
> pointless if you're not just after the extra capacity.
>
> Are there any reasonable choices for bigger (3+ shelf) direct-connected
> RAID10 arrays, or are hideously expensive SANs the only option? I've
> checked out the latest Areca controllers, but the manual available on
> their website states there's a limitation of 32 disks in an array...

In the context of RAID 10, what are the drawbacks of sticking several
such controllers and use them only for hardware RAID 1 arraylets,
running RAID 0 across them in software? You'd lose booting from the
array but data safety should be about the same since the hardware is
mirroring data, right?

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