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Re: Anyone familiar with Apple Xserve RAID

From: Andrew Rawnsley <ronz(at)ravensfield(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: 2004-08-26 20:12:06
Message-ID: 33FEF898-F79C-11D8-8F2F-000A95C1D2E6@ravensfield.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Aug 26, 2004, at 3:54 PM, Doug McNaught wrote:

> Kevin Barnard <kbarnard(at)speedfc(dot)com> writes:
>
>>    Actually you are both are right and wrong.  The XRaid uses
>>    FibreChannel to communicate to the host machine(s).  The Raid
>>    controller is a FibreChannel controller.  After that there is a
>>    FibreChannel to UltraATA conversion for each drive, separate ATA 
>> bus
>>    for each drive.
>>    What I am curious about is if this setup gets around ATA fsync
>>    problems, where the drive reports the write before it is actually
>>    performed.
>
> Good point.
>
> (a) The FC<->ATA unit hopefully has a battery-backed cache, which
>     would make the whole thing more robust against power loss.

Each controller is battery backed (pretty beefy batteries too). 
Actually, they are optional,
but if you spend the money for the unit and leave off the battery you 
should
have your head examined.


> (b) Since Apple is the vendor for the drive units, they can buy ATA
>     drives that don't lie about cache flushes.  Whether they do or not
>     is definitely a question.  ;)

Given what they charge for them I would like to think so...but who 
knows...

The ones in mine are from Hitachi, model #HDS722525VLAT80.

>
> -Doug
> -- 
> Let us cross over the river, and rest under the shade of the trees.
>    --T. J. Jackson, 1863
>
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--------------------

Andrew Rawnsley
President
The Ravensfield Digital Resource Group, Ltd.
(740) 587-0114
www.ravensfield.com


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