Re: Windows XP RAID 5

"Dorothy Bradbury" <dorothybradbury@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:x4%eg.3958$Z7.2634@xxxxxxxxxxxxxxxxxxxxxxx
I assume you have 3-4 disks for data + 1 disk for System?

Got a nice 160 gig drive for the system, and 5 identical 250 gig drives
(bought them all together for a different project :-) )

XP Software RAID can not RAID the System disk...
o Dynamic Disk status required for software RAID
o System Disk can not be set to be a Dynamic Disk
o XP can not RAID the System Disk

That's fine, got a 160 gig drive for system software, swap file and the
like.

Software RAID-5...
o RAID-5 uses parity calculation imposing a load on the CPU
---- specifically it imposes latency due to using the CPU
o Performance can suffer - specifically writes (and suffer a lot)
---- some h/w solutions have poor RAID-5 write performance

The CPU is an Athlon XP 2500+ with pretty much nothing else to do - while it
isn't the worlds fastest processor, I'm sure it can handle the RAID5
calculations quickly enough to satisfy the 100 meg network connection :-)

If critical usage...
o Best -- use 3-ware 4-port card
---- hardware RAID 5 (onboard CPU does the parity calculation)
-------- with 4 disks gives you 750GB for data
---- hardware RAID 10 (Striped & Mirrored)
-------- with 4 disks gives you 500GB for data
o Tolerable -- Promise Fasttrak TX2000, TX4000 etc
---- reasonable RAID card yet quite cheap

For a browse around the RAID solutions go to www.span.com

Network bandwidth...
o 100Mbps is about 9MB/sec bandwidth
---- any hard drive can saturate so RAID offers reliability only
o 1000Mbps is about 88MB/sec bandwidth
---- outer tracks of a Raptor may saturate *if streaming data*
---- RAID-10 of Barracuda may saturate *if streaming data*

When you say the network is 100MB/sec I think you mean 100Mbps.

Absolutely yes. The network could be easily upgraded to 1000Mbps which
would gve some extra room, but the setup Tom was using (admittedly on a much
more powerful CPU system) was capable of kicking out ~150 MB/sec. The
limiting factor would still be the network here, but as I say, speed isn't
that much of a concern.

The application is not likely to demand RAID-striped performance.
o Usage will not demand it
o Network will not provide it re 100Mbps

Which is why Im not keen on RAID 0+1 - half the disk space is wasted, and
the performance gains are not going to be noticed.

If you have 4 disks in total your only choice is...
o 3 disks for Data -- RAID-5 without hot standby
---- limits you to 500GB
o 1 disk for System -- can't be RAID'd as not a Dynamic Disk
---- has its 250GB available

If you have 5 disks in total you could do...
o 4 disks for Data -- RAID-5 with hot standby
---- gives you 750GB
o 1 disk for System -- can't be RAID'd as not a Dynamic Disk
---- has its 250GB available

This is pretty much what I'd like to do. The system disk is only 160 gig,
but the machine won't be getting used for much else anyway, a few drivers
etc are all that would be installed. 750 gig is enough space for the
dataset in question, now and in the future.

Alternatively...

Use 3ware or Promise Fasttrak 4-port h/w RAID card...
o Use all 4 disks in a h/w RAID-5
---- gives you 750GB for system AND data
o System can be installed on there as well
---- so your system has added reliability

This is an option, I'll have a browse for a IDE RAID card. It must be IDE
as theseare the drives I have here, and I don;t want to swap to SATA for no
good reason (not when I have so many good IDE drives anyway :) )


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