Hardware RAID or OS RAID?

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Hi All: I have built up a number of 1U servers that have always had some
flavor of Adaptec controller chip on the mobo, allowing me to configure
RAID0, 1 or 5 in BIOS, and usually I will set up a mirrored array in BIOS
and walk away for a few years <g>. Call me lucky but I haven't had a single
U320 SCSI or even any SATA drives fail yet...powersupplies seem to die
faster than drives in 1U servers.

But, the one limitation of BIOS-controlled RAID mirrors is that if a drive
fails, one needs to shutdown, swap in a new drive, reboot to bios and
rebuild the array. I've experimented with Server2003 mirroring on some
testbed servers and haven't had any problems with that either (e.g. no
drives have failed yet <g>). My thought is that this will allow for
zero-downtime maintenance if swapping a failed mirror drive?

I need to set up some new production servers on Server 2008 Std and/or Web
(using SATA drives), and I'm not sure which way to go for a mirrored boot
array...should I continue to use a BIOS-controlled array or go with
OS-controlled mirror? I haven't seen any "real" real-world analysis of what
(if any) impact on performance OS-based RAID has vs. BIOS-based RAID? Any
thoughts would be appreciated.
 
Re: Hardware RAID or OS RAID?

Most raid adapters have management utilties to reconfigure/manage the arrays
and the card itself. Does not Adaptec have the Storage Manager utility?

"geek-y-guy" <noone@nowhere.com> wrote in message
news:%23IuQ0nNlIHA.5820@TK2MSFTNGP04.phx.gbl...
> Hi All: I have built up a number of 1U servers that have always had some
> flavor of Adaptec controller chip on the mobo, allowing me to configure
> RAID0, 1 or 5 in BIOS, and usually I will set up a mirrored array in BIOS
> and walk away for a few years <g>. Call me lucky but I haven't had a
> single U320 SCSI or even any SATA drives fail yet...powersupplies seem to
> die faster than drives in 1U servers.
>
> But, the one limitation of BIOS-controlled RAID mirrors is that if a drive
> fails, one needs to shutdown, swap in a new drive, reboot to bios and
> rebuild the array. I've experimented with Server2003 mirroring on some
> testbed servers and haven't had any problems with that either (e.g. no
> drives have failed yet <g>). My thought is that this will allow for
> zero-downtime maintenance if swapping a failed mirror drive?
>
> I need to set up some new production servers on Server 2008 Std and/or Web
> (using SATA drives), and I'm not sure which way to go for a mirrored boot
> array...should I continue to use a BIOS-controlled array or go with
> OS-controlled mirror? I haven't seen any "real" real-world analysis of
> what (if any) impact on performance OS-based RAID has vs. BIOS-based RAID?
> Any thoughts would be appreciated.
>
 
Re: Hardware RAID or OS RAID?

Seems like the reports I've seen lean towards the Hardware RAID as it give
more to the CPU to deal with OS/Applications and not worrying about where
the disk data goes.

Most RAID controllers have a Management App that will run in Windows. If the
mobo raid does not, get one that does.

Scott-
"geek-y-guy" <noone@nowhere.com> wrote in message
news:%23IuQ0nNlIHA.5820@TK2MSFTNGP04.phx.gbl...
> Hi All: I have built up a number of 1U servers that have always had some
> flavor of Adaptec controller chip on the mobo, allowing me to configure
> RAID0, 1 or 5 in BIOS, and usually I will set up a mirrored array in BIOS
> and walk away for a few years <g>. Call me lucky but I haven't had a
> single U320 SCSI or even any SATA drives fail yet...powersupplies seem to
> die faster than drives in 1U servers.
>
> But, the one limitation of BIOS-controlled RAID mirrors is that if a drive
> fails, one needs to shutdown, swap in a new drive, reboot to bios and
> rebuild the array. I've experimented with Server2003 mirroring on some
> testbed servers and haven't had any problems with that either (e.g. no
> drives have failed yet <g>). My thought is that this will allow for
> zero-downtime maintenance if swapping a failed mirror drive?
>
> I need to set up some new production servers on Server 2008 Std and/or Web
> (using SATA drives), and I'm not sure which way to go for a mirrored boot
> array...should I continue to use a BIOS-controlled array or go with
> OS-controlled mirror? I haven't seen any "real" real-world analysis of
> what (if any) impact on performance OS-based RAID has vs. BIOS-based RAID?
> Any thoughts would be appreciated.
>
 
Re: Hardware RAID or OS RAID?

geek-y-guy <noone@nowhere.com> wrote:
> Hi All: I have built up a number of 1U servers that have always had
> some flavor of Adaptec controller chip on the mobo, allowing me to
> configure RAID0, 1 or 5 in BIOS, and usually I will set up a mirrored
> array in BIOS and walk away for a few years <g>. Call me lucky but I
> haven't had a single U320 SCSI or even any SATA drives fail
> yet...powersupplies seem to die faster than drives in 1U servers.
>
> But, the one limitation of BIOS-controlled RAID mirrors is that if a
> drive fails, one needs to shutdown, swap in a new drive, reboot to
> bios and rebuild the array. I've experimented with Server2003
> mirroring on some testbed servers and haven't had any problems with
> that either (e.g. no drives have failed yet <g>). My thought is that
> this will allow for zero-downtime maintenance if swapping a failed
> mirror drive?
> I need to set up some new production servers on Server 2008 Std
> and/or Web (using SATA drives), and I'm not sure which way to go for
> a mirrored boot array...should I continue to use a BIOS-controlled
> array or go with OS-controlled mirror? I haven't seen any "real"
> real-world analysis of what (if any) impact on performance OS-based
> RAID has vs. BIOS-based RAID? Any thoughts would be appreciated.

Software RAID stinks - too much overhead on the OS. If you use hotswappable
drives you don't need to shut down. I don't use RAID1, either....and I
always include a hotspare. Just my $.02
 
RE: Hardware RAID or OS RAID?

I've only had one server disk fail in many years of this game, but had two
controllers fail which trashed the connected disks'contents.

Thus I regard mirroring as a useful extra but not a panacea. Duplex
controllers are a better insurance, then if one controller 'knee-jerks' at
least the other disk shouldn't get a kick in the groin.

The other point about RAID is that it may make data recovery harder in the
event the (exotic) controller fails and you have no replacement on-hand. With
JBOD or simple mirroring the disks can usually be read on a standard
controller.

"geek-y-guy" wrote:

> Hi All: I have built up a number of 1U servers that have always had some
> flavor of Adaptec controller chip on the mobo, allowing me to configure
> RAID0, 1 or 5 in BIOS, and usually I will set up a mirrored array in BIOS
> and walk away for a few years <g>. Call me lucky but I haven't had a single
> U320 SCSI or even any SATA drives fail yet...powersupplies seem to die
> faster than drives in 1U servers.
>
 
Re: Hardware RAID or OS RAID?

Anteaus <Anteaus@discussions.microsoft.com> wrote:
> I've only had one server disk fail in many years of this game, but
> had two controllers fail which trashed the connected disks'contents.

Really? I've seen SCSI & SAS drives fail as well as cheapo IDE ones.
>
> Thus I regard mirroring as a useful extra but not a panacea. Duplex
> controllers are a better insurance, then if one controller
> 'knee-jerks' at least the other disk shouldn't get a kick in the
> groin.
>
> The other point about RAID is that it may make data recovery harder
> in the event the (exotic) controller fails and you have no
> replacement on-hand. With JBOD or simple mirroring the disks can
> usually be read on a standard controller.

I use Dell or HP or IBM servers with not-terribly-exotic RAID controllers -
for my small office networks I generally get buy a single RAID5 array.
Sometimes RAID1+0. I always include a global hotspare, and I don't let my
clients buy cheap server hardware or get out of warranty status on
production machines.

This has proven to be money & effort well spent over the years. I have yet
to see a controller go entirely pear shaped.
>
> "geek-y-guy" wrote:
>
>> Hi All: I have built up a number of 1U servers that have always had
>> some flavor of Adaptec controller chip on the mobo, allowing me to
>> configure RAID0, 1 or 5 in BIOS, and usually I will set up a
>> mirrored array in BIOS and walk away for a few years <g>. Call me
>> lucky but I haven't had a single U320 SCSI or even any SATA drives
>> fail yet...powersupplies seem to die faster than drives in 1U
>> servers.
 
Re: Hardware RAID or OS RAID?

geek-y-guy wrote:
> Hi All: I have built up a number of 1U servers that have always had some
> flavor of Adaptec controller chip on the mobo, allowing me to configure
> RAID0, 1 or 5 in BIOS, and usually I will set up a mirrored array in BIOS
> and walk away for a few years <g>. Call me lucky but I haven't had a single
> U320 SCSI or even any SATA drives fail yet...powersupplies seem to die
> faster than drives in 1U servers.
>
> But, the one limitation of BIOS-controlled RAID mirrors is that if a drive
> fails, one needs to shutdown, swap in a new drive, reboot to bios and
> rebuild the array. I've experimented with Server2003 mirroring on some
> testbed servers and haven't had any problems with that either (e.g. no
> drives have failed yet <g>). My thought is that this will allow for
> zero-downtime maintenance if swapping a failed mirror drive?
>
> I need to set up some new production servers on Server 2008 Std and/or Web
> (using SATA drives), and I'm not sure which way to go for a mirrored boot
> array...should I continue to use a BIOS-controlled array or go with
> OS-controlled mirror? I haven't seen any "real" real-world analysis of what
> (if any) impact on performance OS-based RAID has vs. BIOS-based RAID? Any
> thoughts would be appreciated.
>
>
Avoid software RAID at all costs, especially if you already have
hardware RAID available. We had a vendor set up a software RAID array (I
wasn't knowledgeable enough at the time to object). A year later, one of
the hard drives failed AND WE LOST ALL THE DATA!!!

Stick with the hardware RAID.....

--

Regards,
Hank Arnold
Microsoft MVP
Windows Server - Directory Services
 
Re: Hardware RAID or OS RAID?

| > I need to set up some new production servers on Server 2008 Std and/or
Web
| > (using SATA drives), and I'm not sure which way to go for a mirrored
boot
| > array...should I continue to use a BIOS-controlled array or go with
| > OS-controlled mirror? I haven't seen any "real" real-world analysis of
what
| > (if any) impact on performance OS-based RAID has vs. BIOS-based RAID?
Any
| > thoughts would be appreciated.
| >
| >
| Avoid software RAID at all costs, especially if you already have
| hardware RAID available. We had a vendor set up a software RAID array (I
| wasn't knowledgeable enough at the time to object). A year later, one of
| the hard drives failed AND WE LOST ALL THE DATA!!!
|
| Stick with the hardware RAID.....

What kind of RAID system fails when only one drive goes bad?

And when the controller fails, lots of luck recovering the RAID array. Many
of the hardware RAID systems are proprietary, meaning if the controller
fails, you MUST replace the controller with an identical model before you
can access your RAID array. Hardware controllers ARE much faster than
software RAID though. If cash is no object, then be sure to purchase TWO
controllers and stock one away as a spare.

At least with Software RAID you have a much better chance of rebuilding the
array. Software RAID will allow you to change controllers, and even move the
array to a different PC, to increase your chances of recovering data. Speeds
are definately slower on software RAID though.

Home users should invest in RAID5. This allows one drive to fail without
losing your data. Those with really important stuff should use RAID6. RAID6
will still function if two drives fail.

Business users should invest in RAID1, or RAID1+0. This means that every
drive has a mirror. You don't lose your data unless the primary and mirror
drive both fail. RAID 1+0 is the same as RAID1, with a boost in performance.

....and all of these are still susceptible to virii, user error, etc. RAID
only protects you against drive failure.


And, finally, one word of advice. Be sure to LABEL your drives well. If you
have a failure, be sure to check your array after removing the failed drive
to make sure you pulled the correct one!

I built a RAID system a couple years back for a friend - Eight 250gig
(biggest at the time) drives, with a ninth as spare. I phsically labelled
the drives according to the connectors on the RAID controller. There was a
drive failure and he simply swapped the drive out according the label on the
drive and did not check the array afterwards. Needless to say, the array was
still broken and all was lost when a second drive failed.
 
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