Input on RAID 1

I'm in the process of spec'ing a new system and am considering RAID 1 for
data protection against HD failure. The system will be 2.8 P4, 1GB matched
RAM, nVidia 550 or 750 graphics card, and Win XP Pro. I'm looking at
Gigabyte GAk1100 mobo which uses a Intel RAID driver. Does anyone have
experience with RAID 1 and it's effect on performance? Would just
periodically backing up to a slaved non RAID drive a better solution? Any
input welcome

TIA

 

Unless you are using an off motherboard RAID controller and SCSI disks don't
expect much.

Scrutinize the motherboard and chipset used. Look at www.anandtech.com and
www.tomshardware.com or other reputable testing group for information on
which chipsets and motherboards have the best I/O performance. SW pages
alot and memory I/O and cpu performance should be foremost in your mind. A
fast disk system and hot graphics card are secondary. Fast disk is less
important than fast graphics.

 

Raid 1 is slower overall than a HD by itself. It reads faster but since
everything is written twice it averages out slower. I'm also in the process
of spec'ing a new server, which I'll build myself, and Raid 0+1 is the way
to go. No need to go SCSI. The newest 8mb cache IDE drives and Serial ATA
(SATA) drives do very well. Take a look at http://www.xbitlabs.com/ for
some great tests and reviews. The problem with Raid 0+1 is that since it is
"striped" (meaning everything gets read or written to the closest sector,
for lack of a more detailed explanation) and mirrored (meaning everything
gets written twice) it takes 4 HD's! To the uninitiated that's a lot of
wasted money. But the payoff is speed and reliability. HD's are cheap.
The formula is 50% "waste" for Raid 1 or 0+1, meaning half the drives get
used for mirroring. By comparison Raid 0 is no "waste" meaning all the
drives in the array get used for space.

Raid 0+1 is not as fast as Raid 0 but it's nearly as safe as Raid 1. The
speed is somewhere in the middle. I think you'd be really impressed. For
the best safety you could look into Raid 5 which uses 4 HD's in parity,
meaning it's a big striped array similar to R0 but part of each drive "tells
where the data is" so if you lose a drive you can rebuild and keep going.

I've found no motherboard that offers the kind of speed and flexibity that I
want from R0+1 or R5 so I'm going with an external controller running at
66mhz. Most likely the Promise TX4000. You want a controller that offers
as many connectors as you have drives, so if you're doing a R0+1 with 4
drives you want 4 connectors, setting each drive as it's own master.

I've given you enough information, or false information to get you
started. Search the web for the rest and you'll end up fine.

- Eddy

 

We have a machine using RAID 0 which dramatically decreases the seek
time of the drives. I know of someone that has RAID 1 on the mobo (not
using for CAD)and it sucks. The RAID array has to periodically sync
from master to slave so is no better than a separate backup disk. Go
with RAID 0 off the mobo chipset with two 10,000rpm drives (eg. WD
Raptor)and you wont be disappointed.
Good luck.

 

Here's a quick tally of Raid speed/safety assuming equal drives, controller,
etc....

Raid-1 2HD's: Safe but not necessarily fast (Called Mirroring, ~50% waste
for comparison)

Raid-5 4HD's: Safe but faster than R1, slower than 0+1 (One of the most
popular for servers, ~0% waste for comparison)

Raid-0+1 4HD's : Fast and safe, but not as fast as R0 (Called Striped and
Mirrored, ~50% waste for comparison)

Raid-0 2HD's : Extremely fast but not safe; a drive dies you lose
everything (Called Striping, ~0% waste for comparison)

Raid-0 4HD's - Even faster but not safe; a drive dies you lose everything
(Called Striping, ~0% waste for comparison)

Raid-0 8HD's - Yipes fast! but not safe; a drive dies you lose everything
(Called Striping, ~0% waste for comparison)


Incidentally I run R1 in my server now. I want faster speed with good
margin of safety. That's why I am going R0+1 rather than R5.

- Eddy

 

RAID 0 will perform better, for now I'm just looking for data protection.
For just a plain backup, does XP Pro have a backup feature that periodically
copy selected directories to a backup disk at a set time? This might be a
better solution than RAID 1 and lower cost than RAID 0+1 or 5.

 

Well Said Eddie!

My not so useful recommendation - stripe for speed + good daily backup
system. Cache memory on card if possible. Mirroring useful, but not
needed if a good system of backup exists. In my pastlife I had cached
controller and fell in love - extra cache alone made life good and
quited down the drive to a faint whisper - performance improvements
too.

Regards,

SMA

 

we use a tape drive every night. we have 14 tapes so that we can go
back 2 weeks if we need to recover anything.

 

Is it stupid to think of a system with 2x 120 Go HD, 1/3 of it (2x40Go) on
RAID0, the rest being used at night to backup the data on both drives?
(just got one, with 8Mo cache, for home)

--> with no huge extra cost, RAID 0+1

My.01 Eu

JM

 

Windows built in backup, in a word, sucks. Look at "Backup MyPC" from
www.stompinc.com. I use it - it is very good. Backs up to HD, CDRom, DVD,
Tape, etc. It is the desktop version of Veritas Backup Exec.

- Eddy

 

Can you clarify? Are you using only 2 drives for psuedo RAID 0+1 by
partitioning
each drive for RAID 0 and then using a backup program on the remaining part
of the drive ? How is this done and what are the drawbacks?

 

Yes, raid 1 at night

Just a product of my imagination. I am wondering if it could be implemented,
and how.