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Date:      Sat, 19 May 2012 16:30:58 +0200 (CEST)
From:      User Wojtek <wojtek@wojtek.tensor.gdynia.pl>
To:        Robert Bonomi <bonomi@mail.r-bonomi.com>
Cc:        tesla@sunset.tx.net, freebsd-questions@freebsd.org
Subject:   Re: Optiplex 755 RAID 1 logical drive configuration ignored by FreeBSD 9.0-R installation
Message-ID:  <alpine.BSF.2.00.1205191617590.31310@wojtek.tensor.gdynia.pl>
In-Reply-To: <201205191225.q4JCPxkH063784@mail.r-bonomi.com>
References:  <201205191225.q4JCPxkH063784@mail.r-bonomi.com>

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>
> I used 'hardware RAID' because that is -precisely- how the OP described
> their equipment.
unfortunately this is true - it is DESCRIBED as such. lie is standard tool 
in todays IT marketing.

What are facts:

- very few controllers actually have some RAID support. those usually have 
onboard RAM in substantial amount and preferably - battery backed.
- unless you need RAID-5,6 or similar hardware cannot speed it up much.
- gmirror/gstripe in FreeBSD is vastly superior to any RAID including true 
hardware ones - if configured properly. unless you treat single-process 
sequential read as measure of performance.

even graid5 (from ports) is close to, or even outperform true hardware 
RAID, but CPU load is substantial.

- RAID hardware does not allow any flexibility, like partitioning disks 
and using different RAID styles for parts. very useful.

- with FreeBSD software RAID you will be able to access your data in every 
computer with SATA port.

That's simple.

>  And Dell does offer at least one such controller.

Yes true. Actually all recently bought servers i have to manage are Dells 
(yes their 24-hour warranty replacement on place actually work!).

And i always make sure no "hardware" RAID is present :), to get best 
performance.

Actually i told Dell marketer i will be recommending hardware RAID 
solution for Dell when he prove it will actually outperform my 
software RAID10 setup with same amount of same disks. Still not proved ;)

Of course you have to properly configure both "hardware" and software 
RAID.


>

The cases where true hardware RAID may help is it's battery backup 
write-buffer that consume forced syncs (database commits etc) when they 
are common. still if it is an issue it means than database software is 
really badly designed if it have to sync constantly. But if there is no 
choice, today there are simple solutions like small-size SLC flash drive 
or battery backed ramdisk in extreme cases.

> Further, I, personally, have a fairly similar Compaq machine, which has
> hardware RAID, with it's own BIOS (including configuration/setup screens).

what is the chip that you say it is hardware RAID? 
I dare to not believe you, but possibly you are right.



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