RAID 6 vs. RAID 5+hot spare? Online capasity expansion?

[artsi03]

Hi,

I'm planning to build a new RAID system. I'm looking towards of Promise EX8350 controller as it supports RAID 6. However, I have now started to think about RAID 5+1 disk as a hot spare with automatic rebuild.

What do you think? They both should be quite as secure, but RAID 5 is faster? My RAID system is to serve as media center and a NAS with 8 disks, so the security is the top priority (but I'm not willing to spend to that more than 2 drives).

Another question if I may, do you know about online capacity expansion with RAID cards (or specially EX8350)? If I decide to buy 4 HDD's now and split them 100mb to C:\ and 200mb to D:\ - after buying another 4 HDD's to my max, will I still have 100mb on C:\ and 200mb on D:\ and the new space available to allocate as a new drive E:\ OR will this go directly to my old C:\ and D:\ drives to make them twice as big -> 200mb and 400mb?

Thank you for your help!
Artsi

 

[rvnguy]

You will have to investigate if the promise board will allow multiple arrays to determine if you can do what you want.

I have never used a promise card, preferring either Areca or 3Ware.

RAID 6 capacity is n-2 and is usually reserved for arrays with a large # of drives where the capacity becomes less important and the statistics on a double drive failure are higher. At least this was the intent but with the MTBF of the current field of HD's I would stick with RAID 5 especially since you seem to want a 4disk array and then another 4disk array later.

rvnguy
"I know everything..I just can't remember it all

 

[wahnula]

I can vouch for the 3ware 9000 series and RAID 5 + hot spare.

This is a very robust card with excellent US-based support and provides for hot-spare rebuild. Mine is a PCI-X 64-bit 9500s but works fine in a standard 32-bit PCI slot.

If you added another four drives you will need another card, it would show up as a new array and drive letter.

The Promise EX8350 looks like a PCI-Ex1 card, so you would need another avilable PCI-E slot.

Another option would be to replace the original (4) drives with larger ones and restore your data to the larger array, while giving it the same drive letter structure as your old array.

Or just start with bigger drives in the first place.

In either case I would recommend a mobile RAID rack:

http://store.yahoo.com/directron/bpu340sata.html