RAID Question

[Farm]

Just a quick question about RAID.

I have never run a RAID array before. I just bought components for a new system including 2 320 GB 7200.10 drives. With RAID is it possible to run the 2 320GB drives in a RAID array and use another (3rd) drive to run the system?

I guess the main question is can RAID only apply to 2 of the 3 drives?

 

[myocardia]

Yes.

 

[imported_Tick]

Are all three drives identical? If so, you could run RAID 5, (stripping with parity), or RAID 0, (stripping), on them.

 

[Matthias99]

Originally posted by: Tick
Are all three drives identical? If so, you could run RAID 5, (stripping with parity), or RAID 0, (stripping), on them.

Strippers? Where?

Sorry, getting a little punchy. Time for bed.

 

[AstroGuardian]

Yes you can arrange a array with those two disks.

 

[Fullmetal Chocobo]

Yes, you can RAID two disks, and leave one disk alone. Easiest way to have RAID, and avoid the F6 Windows install.

 

[ch33zw1z]

Still may need those drivers to run even one drive.

enjoy your RAID1, i know i do

 

[Farm]

2 of the drives are 320GB Seagate 7200.10. I have several choices for the third drive. If needed, I can use another 320GB drive. I also have a 250GB 7200.9 and a few smaller drives yet.

My thought was that I could benefit from the speed of the 2 320gb's in RAID-0 for reading/writing with large video and photo processing. I could then use another drive for all of the system files.

I'm not as familiar with RAID 5. Does the parity drive need to be the same size as the other 2 drives in order to run RAID 5?

 

[Ilikepiedoyou]

What does setting up a RAID array do?

 

[ch33zw1z]

the quickie google search:

http://en.wikipedia.org/wiki/Redundant_array_of_independent_disks

Basically, it's designed to ensure data redundancy and speed.

 

[dakels]

A RAID is set up for either speed, or backup insurance (parity), or both. It all comes with added cost and/or risk over a normal drive setup. You can RAID whatever you want on multiple drives, 2 of 3 drives, 3 of 3, 2 of 5, etc. You can run RAID 0 on those 2 drives like you said. A third drive can either give you parity (RAID 5) if it is big enough to handle the stripe size. In a RAID 5 2x drives worth of storage is used for speed and 1 drive of storage is used for parity data which will allow a complete restore of those 2 (or more) drives if they fail. Generally, for every 2 drives you need 1 parity drive. The Drive size can be flexible. You would use the smallest drive to create the stripe. Meaning you can RAID a 250gb with 2 320gb drives by creating the stripe based on the 250gb. So RAID 0 would be 250gb partitions across the 2-3 drives, or 2x 250gb partitions with a 250gb parity.

Quick summary of benefits is RAID 0 gives you speed. RAID 5 gives you that speed with backup insurance (parity) should those drives fail. While striping data across those drives give you speed, 1 drive failure means they all fail, hence the risk.

No striping on 3 drives (1 = data):

1|0|0
1|0|0
1|0|0

Striping:
1|1|1
0|0|0
0|0|0

As you can see the stripe spreads data across those multiple drives. This allows 3 to work at once, giving you that speed difference.

RAID 5 is a bit slower then RAID 0 because it needs to write that backup data but both are generally faster then no striping at all. You have to ask yourself if the risk is worth the reward of performance where in most cases that performance might only be 5-20% for home users. Large file users like video/audio editors benefit more from RAID striping. These are just general basics, there are alot of RAID schemas for difference needs/situations. RAID on the main OS drives can also be a bit of a pain so some people do 1 normal drive for the OS and applications, then striping 2 others for data storage/cache. Others do the opposite doing a RAID stripe on the OS/application partition for speed, then normal drive for data storage. All depends on what you need/want.

 

[MerlinRML]

Dakkel's information has a few mistakes. I don't mean to be repetitive.

In regards to using different sized/speed drives, you will be limited to using the smallest drive's size. So if your smallest drive is 250GB, then anything above that would be wasted on the drives that are larger than 250GB.

RAID 0 = striping which writes data across any 2 or more disks. This gives a speed increase due to having multiple hard drives to read from and write to at once. It has a drawback in that the failure of one drives means all the data is lost (and by using multiple drives, your chance of failures increase). There is no redundancy for this RAID type and is considered risky for any critical data. The more disks you have in a single RAID array, the better your performance but the higher your chances for failure.

RAID 1 = mirroring which gives no performance increase but gives you hardware redundancy by copying all data from one drive to a second driveand if one of the drives fail there is an exact "mirror" which you can use to replace the failed drive. This is a perfect form of redundancy as every drive has a replacement on hand, but it gets very expensive as you have to purchase a second disk for every hard disk to achieve this redundancy.

RAID 5 = striping with parity which is similar to RAID 0 in that your data is written across multiple disks (3 or more disks for RAID 5). In addition to the data, there is parity information that is written across all the disks as well. It is the parity information that gives you hardware redundancy so if a single disk fails, you can replace that disk and rebuild the data from the parity information stored on the other disks. The remaining disks run in "degraded" mode while there is a disk failure. You sacrifice space on each disk for the parity information, and you effectively give up one entire disk's worth of space. This is a very popular form of RAID as you only sacrifice a single disk's worth of space and still get hardware redundancy. RAID 5 can also provie an increase in read and write performance, with the amount being dependent on the number of drives you have available.

Check to see which RAID levels are available to you (determined by your RAID controller) and which one makes the most sense for you to use.

Another issue of note is that RAID is not a backup for your data. It is a backup for your hardware. If you get a virus, or if your operating system gets corrupted, or if you accidentally delete a file, that change happens on every hard disk. RAID is not a data backup, it is a hardware backup. If you want a data backup, you need another mechanism in addition to your primary storage.

 

[Farm]

So what would be better if price were not an obstacle?

1) Get a 3rd 320GB Seagate 7200.10 and run a total of 3 drives in RAID 5
- what is the total storage space in RAID 5? Is it 66% of the system total due to the parity?
- This would be the cheaper option

2) Get a separate WD Raptor (150GB probably) and run the system off of it and use the other 2 x 320GB Seagates in RAID 1
- Total system storage space is only 470GB vs. option 1
- Would this be noticeably faster?


I like the idea of parity so that I have a decent backup system in place. I usually backup the entire system to DVD or external drive monthly.

Thanks for all the replies so far.