raid5 space question

[dvd_maniac]

I just purchased 4 250GB Maxtor 16MB Cache, 7200rpm, 133ATA hard drives that are on sale at CompUSA for $99 until February 26th. I am looking at the Promise sx4060 for a raid5 card. I use WinXP Pro with 64kb block size and NTFS.
My question is how much space would the resulting hard drive be?
IE: How much space is used for parity & system, and how much is left for NTFS partition?

[weetbix]

For every stripe across your disks in a RAID 5 set you have one of the drives storing parity for the stripe and the other drives storing the real data. Therefore you for the RAID 5 set you will take up the equivalent of 1 disk for parity.
eg for each drive the stripe would be like
1 2 3 4
D D D P
D D P D
D P D D
P D D D
and so on.

So in theory you would have 750GB of diskspace with your 4 drives. Allowing for the fact that disk sizes are reported using 1,000,000,000 bytes instead of 1,073,741,824 bytes (1024*1024*1024) you would probably end up with around 730GB of usable diskspace before creating any NTFS partitions. These would then add their own overheads reducing the actual usable capacity further (should be by much though).

Nice to have for home :)

[The Belgain]

Yup. The capacity for a RAID5 array is (n-1)*(size of smallest drive), so 750GB minus overheads in your case.

I've similarly gone down the RAID5 route and so far, am very happy with it (though I haven't had any drives fail yet, so it's not proved necessary...).

[dvd_maniac]

I was wondering if someone can answer an upgrade question for me.
I have 4x250GB drives on my SX4060 Promise raid-5 card and would like to upgrade to 4x400GB. The 750GB raid-5 I have now is close to full. There is no easy way to backup this much data and the Promise website says that I can't upgrade the drives size seamlessly. So if I replace one drive at a time from 250 - 400GB after all 4 was replaced I would still only have 750GB minus overhead (710GB).

My question is whether or not a disk application like Partition Magic would allow me to expand it?

[em64t]

Can you possibly get an additional RAID controller ... at least temporarily. Clone the 4x250 GB to 4x400 GB using Partition Magic and the partition copy feature. Try at your own risk. Details below.

Yes, if you replace one disk at a time, the result is as you have written. But then you will have 4x150 GB unpartitioned space. The easy way is why not just create an additional 4x150 GB partition?

I just checked Partition Magic info online. I am not sure I would trust it if Symantec does not. Symantec says the limit on Partition Magic is only 300 GB. Read here (http://www.powerquest.com/partitionmagic/features.html).

@The Belgian:

Yes one of the benefits of RAID 5 is data integrity. Another is performance. So it is still good to have RAID 5. :-)

[weetbix]

Most RAID controllers I have dealt with (which have been SCSI based and in the server arena) do not allow you to upgrade the drive sizes. If you substitute a larger drive for one of the current drives the array controller will only allocate the capacity of the smaller drives on the bigger disk. The unallocated space is not available even if you went and upgraded all the drives in the array.

I think your best option would be as em64t mentioned and try and get another RAID controller. Of course if it is not exactly the same type of controller you will not be able to swap the new drives back to your original controller as it won't recognise the array set.

[dvd_maniac]

I have a couple 200GB drives laying around and will borrow a buddies 250GB. That will allow me to backup all my data and put the new drives in and copy it back.

Unfortunately, I could not get another Raid card to work with the 4060 in the machine. I tried to take everything else out and just have the 2 4060's in there with just video card. No dvd-r, cd-rom, HHD, TV Tuners. And NO BOOT! It wouldn't even boot with the 1 4060 and the on board sata raid controller enabled.

P4C800 E-Deluxe for a motherboard.

Oh well, problem solved. Next time I will look deeper into the whitesheets before buying a raid-5 card..

[dvd_maniac]

Can anybody tell me what performance difference I should see when upgrading the Promise sx4060 from 64MB to 256MB?

I mainly use it for video storage. Most of my movies are either in Nero Digital ASP/AVC or xvid at about 650MB per 2 hour movie.
This 4x250GB (Soon to be 4x400GB) also house my WinXP Pro OS.

Should I see an improvement worth mentioning? Or would the extra memory really not do anything for me and would be more suited for Server applications?