What RAID setup?

I have searched around and have read some of the suggestions.

I would like some input from the server specialist here.

What RAID is better RAID-0 or RAID-5?

I know losing one disk will take out server.

My main question is which one is more efficient and/or faster?

RAID-0 but it has no redundancy... if one disk fails, all info is lost from those drives.  There is a RAID-10 which is a combination of RAID 1 + 0 (RAID-1 = mirrored drives).  I use RAID-1 on all my home servers... two sets of RAID-1 drives with the OS on the first set and the DB on the second set.  With a good RAID controller you should get simultaneous 'reads' (different data) happening on each of the mirrored drives.

Raid 0 is faster than raid 5.

Raid 0 is striping. Requires a min of 2 disks. Data distributed across both disks. A loss of one disk is the same as a one disk system. All data is lost. So it is not a system for redundancy. It's designed to increase capacity making multiple disks appear as one disk.

Raid 5. Requires a min of 3 disks. Less storage capacity then Raid 0 because space equal to the size of one disk  is used for parity checking. Hence the reason it's performance is slower. But raid 5 also is redundant. The loss of one disk will not cause loss of data. Just replace the disk and rebuild the array and your back up and running.

Yes. As epaulo mentioned. Raid 10 is both striping and mirroring. So it has fast performance and redundancy. If it is an option for you than it is considered the best option. Requires a min of 4 disks. Not widely used as it's also the most expensive option.

I haven't researched RAID setups for a couple of years but when I did, from my perspective, the hard drives were relatively cheap compared to quality RAID controllers.  In my opinion, to really get top performance, you need a very good RAID Controller.

Thanks so much for the quick and great explanation of the setup.

I know the units are older but... they are Dell PE 2650's I got two of them for 76 bucks so I couldn't resist picking them up to teach myself on.

Now, I see one has one drive, 76gb so that one is not being set up that way. It is hosting my home site.

The other one, has five drives at 36gb each, and a SCSI addon card allowing for I guess four more external drives from the card. It is the one with several options in the RAID where I get a bit lost, it's the one I'm learning on.

Should I have two drives for the system, two that mirror those two and the fifth one for?..

Right now it is setup with 5 me 140 something gb, one disk, I do notice it is slower than when I had it configured at 0.

EPaulo,  10 is not an option I think with these beast.

It is the PE expandable RAID controller card add in for this server.

The RAID manager says PERC/CERC

and what is HSP (HotSpareDevice)

Those were very nice servers in their day... I've used them.  Do you eventually plan to run both of them or use one for spare parts?  I'd check both servers and all the drives to ensure they're performing at full specs... depending how many components are working at full potential, I'd then decided which RAID system to setup.  If you only need one server I'd be inclined to make the best single server you can... leaving the remainder for spare parts.  If you're not worried about the site going down for a day or two then you could run RAID-0 on one sets of 2x36GB drives with nightly backup to the 76GB drive.  With 5 working 36GB drives I'd be tempted to setup a RAID-5 using 4 drives... plus a hotspare... and use the 76GB for non-essential and temp files.  Backup to an external drive.  This would give you about 100GB of RAID space to use. 

The problem with running RAID-1 on such small drives is you don't end up with much space.  So, yes, you should be able to run two sets of RAID-1 drives (using 2x2x36GB HDD) but you will be restricted to two visible drives of 36GB.  You'll need to budget what you load onto those drives.  It's a bit of a guessing game on how to make the best use of the two visible drives but loading Apache on one and MySQL on the other would be good.

I imagine you've looked it up by now but a hotspare drive is essentially an extra (powered but inactive) hard drive that's always available to replace a failing RAID hard drive.  It's essentially passive protection against two successive (but not simultaneous) HD failures.  In other words, if a RAID-5 without a hotspare has a HD failure then the RAID is vulnerable to losing all data if another drive fails before a replacement HD can be manually added. 

The primary reason I suggest you keep one 36GB drive as a hotspare is because you may have trouble finding a matching 36GB SCSI drive "quickly" if one of yours fails.  I would estimate those drives are at least 10 years old... and that's "old age" for even a quality SCSI drive... especially if they spin at 15k.

 That's exactly the info I was after, thanks. Sorry for delay, was away for a while.

I'm going for one working one, and one for spare as you suggested eventually.

Using the 76gb in the online unit now.

I have the one with the RAID setup on the bench testing the drives, yes they are old, four 10ks and one 15k.

I have it setup now with RAID-5 using all drives. 146gb

My goal is to use 4 four drives 4x36 RAID-5 and the spare 36 as the hotspare.

I'm sure I will be buying new drives eventually. 

If I understand that; one drive is going down the hotspare will populate the data for switch over?

I just looked at the h/w specs and you only have 5 hard drive bays so if you wish to eventually run a RAID-5 with four 36GB drives for important data --and-- the 76GB drive for non-essential data then you might consider going without a 'hotspare'.  The server, as I remember them, has a warning light (and audio alarm?) that will warn you of a failed hard drive (plus you can setup monitoring s/w to email you about system problems).  Since this is a home server, and you'll probably be close by, then you should be okay with a "cold-spare". 

If all the 36GB drives are working at full spec then consider using the 15k drive as the spare... for symmetry reasons. 

I'm guessing you have one processor in each server... when you combine them you can place both CPUs in one server... and install as much *matching* RAM as possible.  I think you'll see some nice performance when it's loaded. 

I wish I could suggest an easy way to test the power supplies... to pick the best one.

I'm stating the obvious but make sure all the cooling fans are working.  The 'loaded' server will generate a lot of heat.  Also, if you can't keep the air in front cool then at the least find a good way to vent the heat coming off the back so as little as possible gets recirculate into the front again. 

Have fun!  After combining the two servers, I imagine you'll have a nice low-cost home server to play with.

Are you running CentOS?

If all the 36GB drives are working at full spec then consider using the 15k drive as the spare... for symmetry reasons.That's exactly the setup I did, RAID-5. I did make the 15k the hotswap. 

The alarms work and I tested all night last night. All fans work on both as well as all four power supplies seem fine too.

The one running now has two 2.0GHz Xeon's CPU's with 3GB RAM with the 76GB

This one will be off, as is in case of the other one going down. Both work perfect.

The one on bench has add on card, two 3.2GHz Xeon's CPS's with 5GB RAM, (plan on getting 2GBx6 to give me 12GB from ebay)

The sound and cooling issues are fine, they are in my "man cave" which has it's own cooling A/C, and is separate from the main house.. suppose in the winter I will not need a heater in there.. lol

The servers run Ubuntu 12.04 Precise LTS.

I don't care for CentOS..

You have been a great in helping me understand these better, Thanks.

 RAID is a waste of time any more, invest in SolidState Drives, and use a NAS to backup to. 

DosDawg, do you offer dedicated server hosting without some form of RAID protection? 

I use RAID-1 for my computers.  HDD are relatively cheap compared to the 'cost' of having a computer down until a replacement HDD is installed and imaged.  Would I say RAID-1 is a must have?... No, not if you have a good backup system in place.

I also like SSD but, due to their expense and size limits, I tend to use them primarily for info where access speed is important.  As for NAS units, I agree they are great for home networks... I have two.  I also use "instant" online backup storage... very good for files that I'm editing often as it provides a set of versions in case I need to roll back after finding a code bug that I can't solve (or realize my code logic for the last hour was wrong!).

 I'm not out to make the best server in the world, I have two PowerEdge servers to play with.

I'm not investing in new servers especially solid state devices.

I happen on these servers on ebay.

Actual price was $41.00 for the  2650 dual 3.2GHz plus $35 for shipping.

The poor guy was new at ebay and they sent a 2.0GHz 2650 instead and had to correct the order to get paid.

He sent a long letter saying he was sorry he didn't ship the first one and would be happy to send the correct one for free!!

So I'm not out to do anything but experiments, and teaching myself.