Adventageous? RAID 10 vs. RAID 1

[blindbug]

I did a search, but found most results talked about the differences between RAID 1 and RAID 10, or said that it depends on the application. Well, I would like some advice on which setup would be best.

We (me and a friend) have a Server in our local network where we house media files for all in the house (currently: (3) computers, (2) xbox... soon to include an Xbox 360, and a HTPC). I currently have a 400GB external Seagate drive hanging off the server, but the spin-up time for trying to access stuff on it when idle is atrocious, hence why we are going internal. We also have some bad wiring in the house and get power surges so we have installed a UPS to assure uptime and protect the server.

We have looked into getting (4) 400GB hard drives with intentions of going with a RAID 1 OR a RAID 10 setup on these drives, but are still up in the air. The reason we came down to these two arrangements is because we have lost the data on the 400GB drive once already due to a power surge and do not want to lose our media again.

Is there any great benefit to having a raid 10 setup as opposed to a raid 1? The reason I ask is because we will eventually be moving out away from each other and if we setup a RAID 1, I believe it is possible for us to each have a copy of our media files. Meaning, we have drives A, B, X & Y... with A & B as the primary drive and X & Y as the backup mirrors. Take X & Y off the RAID setup, so we each have a copy of the media (me having A & B, he having X & Y), is this possible?

Otherwise, would there be a better setup in this situation?

 

[Rocco123]

RAID 0+1 or 1+0 is good if you have the disks and you are willing to sacrafice 2 disks worth of space while doing it.

Although I want to comment on the reasoning for this. If you are worried about power surges, these RAID formats, or any RAID for that matter won't help. If the power surge fried one disk, it would probably fry all 4 if they are in the same physical box. Redundancy is much different than having active backups.

A good technique would be to have a RAID 1 as a base, then have another drive in another box act as a backup. Make sure the other box is wired to a different circuit in your house, if power surges/dips are what you are worried about.

 

[unhappy_mage]

Raid 5. You don't need speed for media storage, especially when it's being accessed over LAN only.

 

[blindbug]

RAID 0+1 or 1+0 is good if you have the disks and you are willing to sacrafice 2 disks worth of space while doing it.

Although I want to comment on the reasoning for this. If you are worried about power surges, these RAID formats, or any RAID for that matter won't help. If the power surge fried one disk, it would probably fry all 4 if they are in the same physical box. Redundancy is much different than having active backups.

A good technique would be to have a RAID 1 as a base, then have another drive in another box act as a backup. Make sure the other box is wired to a different circuit in your house, if power surges/dips are what you are worried about.

I should clarify that we are looking for more redundancy than protection against the power surges (I stated about the power surges just to re-iterate that we have lost data before and don't want to feel that sting again). We are protecting against power surges with a good UPS, but need to make sure that we are protected on redundancy.

We are willing to sacrifice an amount of disk space in order to achieve a good backup of all data (the media is constantly growing and changing, otherwise we backup to DVD every week or so, but because of the nature it is really hard to identify what data is new, and what data has changed).

I will be moving the external drive to my desktop which is on a seperate circuit and I will use to backup what I deem as the most important 400GB of data to further prevent loss and to access it locally when the LAN is being hammered.

 

[blindbug]

Raid 5. You don't need speed for media storage, especially when it's being accessed over LAN only.

The problem I have with RAID 5 is that we will be breaking the RAID once we move out away from each other. Correct me if I am wrong, but in using a RAID 1, the data is mirrored and therefore once we move away from each other, we can each take a set of the 400GB drives, because the sets will be identical and still functional by themselves...

I.E.

We have Disk A & B, 1 & 2...

A & B - Primary Disks
1 & 2 - Backups of A & B

When we part, I will take disks A & B and install them in my own computer, and he will take disks 1 & 2 and install them in his own computer. We will now each have identical working copies of the data on the disks up until the point we split the RAID up.

 

[Zamboni]

Or have A and B as RAID-1 for redundancy, but drives C and D are non-raid. The backup software copies AB to both C and D every night, so either C or D can be used to rebuild a new system if someone moves out. This still leaves the AB system intact, as it won't even notice if the backup drives are removed.

 

[blindbug]

Or have A and B as RAID-1 for redundancy, but drives C and D are non-raid. The backup software copies AB to both C and D every night, so either C or D can be used to rebuild a new system if someone moves out. This still leaves the AB system intact, as it won't even notice if the backup drives are removed.

Again, correct me if I am wrong, but wouldn't this mean that we would only have 400GB of 'usable' space (400GB main, RAID 1 mirror, (2) drives mirroring those (2))? Don't you mean umm... RAID 5?

 

[unhappy_mage]

The problem I have with RAID 5 is that we will be breaking the RAID once we move out away from each other. Correct me if I am wrong, but in using a RAID 1, the data is mirrored and therefore once we move away from each other, we can each take a set of the 400GB drives, because the sets will be identical and still functional by themselves...

Yes, if you both have identical controllers. My suggestion would be against using raid like this, though - you'd both have degraded arrays at that point, no redundancy, and bad things like that. Maybe you could set up a raid 5 now with 3 disks, and when he's moving out (and 400GB drives are hopefully cheaper!) buy 3 more (or 2 if he wants *shudder* raid 0) and copy everything manually.

 

[blindbug]

Yes, if you both have identical controllers. My suggestion would be against using raid like this, though - you'd both have degraded arrays at that point, no redundancy, and bad things like that. Maybe you could set up a raid 5 now with 3 disks, and when he's moving out (and 400GB drives are hopefully cheaper!) buy 3 more (or 2 if he wants *shudder* raid 0) and copy everything manually.

Hrrrm... had not actually thought about that.

Would we need to have identical RAID cards in order to accomplish this? or as long as both RAID cards accept RAID 5, it will build correctly? OR, and I think this is what you mean, create the second box with RAID 5, and then when it's created, copy the information from BOX 1 to BOX 2?

This would probably be a great solution too since we still need to buy a RAID card, it would take less electricity, and would be almost as reliable (in terms of how safe data is).

 

[unhappy_mage]

That's the idea, yeah. Multiple raid cards (notice they don't have to be the same kind!) in multiple machines.

 

[space_monkey]

Would we need to have identical RAID cards in order to accomplish this? or as long as both RAID cards accept RAID 5, it will build correctly?

We have one server that was running RAID 0+1, 4 disks on a Promise SATA. Apparently the guy sitting at that station had turned off the email and window popup notifications generated by Promise Array Management. He had been complaining for the last couple of weeks that his build process kept failing\, with no explanation as to why. Two weeks ago he left for vacation, and so I took this opportunity to look in the logs... PAM was reporting ECC errors on disk 3 going as far back as 2004, then disk 1 started complaining, then disk 4, then SMART errors on 3 and 1, then disk 3 failed and was kicked out of the array... but the guy using the computer had no idea any of this was happening.

This machine is also the company's Exchange / DHCP / Active Directory / Domain controller / CVS repository.

In the end [luckily] I was able to rebuild the array using disks 1 and 2, which between them had 14 bad sectors, so only a couple of non-critical files were lost. He had no backups.

The moral of the story here kids, is that
RAID is a waste of money unless you are also:
1) backing up your data automatically, or at least whenever your important data is preserved.
2) TURN ON your array health monitoring notification!!!

To answer your question about identical RAID controllers, I have been told by Promise support that it would be advisable to use exactly the same controller card model, but I have heard that it is possible to switch controllers and keep your array. This seems reasonable since the information about the array (number of disks, block size, RAID level, size) is stored [redundantly] in the reserved sector near the end of each of the hard disks in the array. In this way, you can swap the order of the disks as they are plugged into your controller and the array will still mount regardless. Your mileage may vary, of course.

 

[Zamboni]

Again, correct me if I am wrong, but wouldn't this mean that we would only have 400GB of 'usable' space (400GB main, RAID 1 mirror, (2) drives mirroring those (2))? Don't you mean umm... RAID 5?

Nope. RAID 1 with removable backups. I wouldn't risk that much data by relying on the new computer to correctly recognize a transplanted RAID-O array. I've seen people lose the entire package when something borks up on the new system. I've found it works easier to use non-RAID drives as backup, then copy the data to a new array.

I personally would use a 3-drive RAID-5 array, and just copy the data over the network to the second machine when the time comes. Far fewer chances of something going wrong along the way, and the hardware on the second box doesn't have to match the first.

 

[space_monkey]

Would we need to have identical RAID cards in order to accomplish this? or as long as both RAID cards accept RAID 5, it will build correctly?

From the user manual of one of my Promise RAID controller cards:
"Q: I already have an array on an older FastTrak controller. Can I move that
array to my new FastTrak S150 TX4 controller?
A: Yes. All FastTrak controllers read the arrays the same way and can be
moved from one controller to another."