scsi + ata raid with Windows Server 2003?

[Tim Mackey]

hi
i'm a newbie when it comes to raid. i've just bought a dell poweredge 1800sc
(for ?149 + tax!) and it comes with an ATA 80gb drive. it's for a web
server, so i want some kind of raid, i'm not too crazy about performance
because it will be very under-utilised. the motherboard has an on-board
single channel U320 scsi controller, so i presume this means it will allow
only one scsi drive plugged into the motherboard. i would like to buy a
36gb 10000 rpm scsi cheetah and set up a 36gb matching partition on the ATA
drive, with software raid done by windows server 2003. (i want to save a
few bucks by not buying any controller cards, and keeping the ATA drive). i
could then use the rest of the ATA drive as a backup partition. is this: a)
possible, b) a good idea?
i've read that OS managed raid can be hard to recover from in case of
disaster.

i really appreciate any advice. thanks in advance.
tim.

\\ email: tim at mackey dot ie //
\\ blog: http://tim.mackey.ie //
67d0ebfec70e8db3

 

[J. Clarke]

hi
i'm a newbie when it comes to raid. i've just bought a dell poweredge
1800sc
(for ?149 + tax!) and it comes with an ATA 80gb drive. it's for a web
server, so i want some kind of raid, i'm not too crazy about performance
because it will be very under-utilised. the motherboard has an on-board
single channel U320 scsi controller, so i presume this means it will allow
only one scsi drive plugged into the motherboard.

Nope. SCSI supports 15 drives per channel.

i would like to buy a
36gb 10000 rpm scsi cheetah and set up a 36gb matching partition on the
ATA
drive, with software raid done by windows server 2003. (i want to save a
few bucks by not buying any controller cards, and keeping the ATA drive).
i
could then use the rest of the ATA drive as a backup partition. is this:
a) possible,
Yes.

b) a good idea?

Why have a backup partition on the same drive as a member of the RAID?
Whatever kills the RAID will kill your backup as well. Use two SCSI drives
for the RAID and put the backup drive in a removable tray and you'll have
somethin a good deal more secure.

i've read that OS managed raid can be hard to recover from in case of
disaster.

The boot drive will be mirrored (RAID 1). That should recover just fine.
It's the striped RAID levels that are hard to recover.

 

[Tim Mackey]

hi john,
thanks for the reply.
i forgot to mention that RAID 1 is the configuration i would use, as you
guessed.
i'm still undecided about using the ATA drive in the RAID, or getting 2 scsi
drives as you suggest. only getting one drive would save me 100 bucks which
is something at the moment.
to me its not the end of the world if my ATA drive crashes losing some
backups, because i still have the original files on the SCSI drive. i would
do occassional off-site backups anyway. would there be a big performance
hit by using mis-matched drives in RAID 1 like a SCSI 10000rpm and an
ATA-100 7200 rpm? i don't want to have the scsi disk waiting around for the
ATA one, if it would defeat the purpose of getting a decent scsi drive in
the first place.

since budget is an issue, an option may be to start with SCSI + ATA in raid
1 and then upgrade in a few months with a second identical scsi drive, move
the ATA out of the RAID and replace it with the new scsi disk. is this an
easy thing to do? can i just plug in the new SCSI disk (chained off the
existing scsi disk) and the somehow the new disk will mirror the original?
i've been brought up on ATA and more recently SATA so there a few gaps in my
thinking of how it all fits together.
thanks for your patience.
tim

 

[J. Clarke]

hi john,
thanks for the reply.
i forgot to mention that RAID 1 is the configuration i would use, as you
guessed.
i'm still undecided about using the ATA drive in the RAID, or getting 2
scsi drives as you suggest. only getting one drive would save me 100 bucks
which is something at the moment.
to me its not the end of the world if my ATA drive crashes losing some
backups, because i still have the original files on the SCSI drive.

Drive failure is not the only reason to do backups. A virus that hits your
RAID would in the configuration you describe also kill the backups. To
take one example.

RAID isn't a backup system, it's a reliability system. The two serve
different purposes.

i
would
do occassional off-site backups anyway. would there be a big performance
hit by using mis-matched drives in RAID 1 like a SCSI 10000rpm and an
ATA-100 7200 rpm? i don't want to have the scsi disk waiting around for
the ATA one, if it would defeat the purpose of getting a decent scsi drive
in the first place.

There won't be a performance hit per se, but the array may spend a good deal
of time unsynchronized.

since budget is an issue, an option may be to start with SCSI + ATA in
raid 1 and then upgrade in a few months with a second identical scsi
drive, move
the ATA out of the RAID and replace it with the new scsi disk. is this an
easy thing to do? can i just plug in the new SCSI disk (chained off the
existing scsi disk) and the somehow the new disk will mirror the original?

You'll have to rebuild the array with the new drive, after that it should
more or less take care of itself.

 

[Odie Ferrous]

The boot drive will be mirrored (RAID 1). That should recover just fine.
It's the striped RAID levels that are hard to recover.

How does one set up OS-controlled RAID on a boot partition? Or were you
referring to the hardware raid option?


Odie

 

[J. Clarke]

How does one set up OS-controlled RAID on a boot partition? Or were you
referring to the hardware raid option?

Once the OS is installed on one drive, you mirror that drive, after that as
long as the OS keeps the two in sync you're RAIDed.

 

[Odie Ferrous]

Once the OS is installed on one drive, you mirror that drive, after that as
long as the OS keeps the two in sync you're RAIDed.

Ok, that bit is easy, but with hardware RAID 1 you will see quicker
reads (and hence quicker boot times) than a single drive.

I know this would not be the case in software RAID - but what about once
the OS has booted?


Odie

 

[J. Clarke]

Ok, that bit is easy, but with hardware RAID 1 you will see quicker
reads (and hence quicker boot times) than a single drive.

After the RAID controller BIOS has initialized, which generally takes long
enough to negate any slight advantage. While there can be a performance
gain from RAID 1 it is tiny and mainly comes from alternating seeks between
the two drives. Personally I've never noticed any performance gain from
RAID 1, and generally the boot time from power on has been extended, not
shortened.

I know this would not be the case in software RAID - but what about once
the OS has booted?

Really depends on how well the OS implements RAID. In practice Windows
software RAID tends to perform on a par with or slightly better than the
low priced "hardware" solutions.