SATA Raid

[Ted Mittelstaedt]

>Most of the cheaper cards just employ software raid,

This isn't accurate.  All cards, even so-called hardware raid cards, use
software
in their firmware.

"software raid" refers to when the host CPU is doing the raid management,
and that
isn't what is happening with chips like the promise, highpoint, and intel
ich that I
posted.  Those chips are mirroring/striping only, and do not offer raid 5
so there
is no parity calculation going on.  Instead, when the driver does a write
to the
chipset, the chipset duplicates the write between the disks.  That is the
same
principle as the bigger and more powerful hardware raid cards like the
compaq/hp
intelligent array controller when they are in raid0

The only significant difference between a real raid card like the
HP/Compaq
intelligent array controller and the cheaper raid chipsets is that you
cannot
attach the cheaper ata raid chipsets to hot-swap disk drive cages, and
pull out one of the hard drives while the server is in operation, replace
it,
and have the raid controller detect all this and silently rebuild the
array
without interrupting reads and writes to the host operating system.
Instead,
if a disk drive dies, you have to shut the server down, replace the
drive,
and reboot into the BIOS so you can run the utility that rebuilds the
array.

Ted

>-----Original Message-----
>From: owner-freebsd-questions at freebsd.org
>[mailto:owner-freebsd-questions at freebsd.org]On Behalf Of Derek Ragona
>Sent: Saturday, February 11, 2006 5:40 AM
>To: Robert Uzzi; freebsd-questions at freebsd.org
>Subject: Re: SATA Raid
>
>
>Be wary of any of the cheaper SATA RAID using si chips, there have been
>many problems noted you will find searching this list and the
>list for current.
>
>I had a lot of problems with an adaptec card that used one of
>those chips.
>
>Most of the cheaper cards just employ software raid, which is
>usually fine
>unless you need higher performance.
>
>Soren is the one to answer on what works well beyond the hardware list.
>
>Hope this helps.
>
>         -Derek
>
>
>At 09:35 PM 2/10/2006, Robert Uzzi wrote:
>>Anyone know of any of the cheaper SATA raid cards that work well under
>>FreeBSD. I'd love to go get a 3ware but they are fairly pricey.
>>
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