To RAID, or not to RAID

[N3St]

Hi all,

I am looking for a new system and was able to decide on all components but the hard drive. I will use the pc mostly for professional purposes (FEM Analyses, Matlab, Photoshop) and games. These programs and games would in case of an SSD most likely not be installed on said SSD due to the package sizes. In my opinion, large SSD's are still on the expensive side and do not provide me with, what I find, worthwhile results because I can wait for windows to start up. Therefore I was looking for another way for an overall speed increase of my system and now I am considering RAID 0 and RAID 5 7200rpm HDD configurations, that theoretically would give my system a noticeable boost (at least for sequential files) and possibly add some redundancy.

What I would like to know is if anyone has noticed any difference in overall pc performance due to the RAID approach and if anyone has suggestions on possible alternatives (including backup/redundancy for the system).

I read this forum a lot and I value everyone's opinion, but if possible I would like to omit the failure probability of RAID 0 systems because about 99% of the forums I've read have reactions on them showing that the majority of people that may know a lot about pc's, may not have familiarized themselves with proper probability theory

Thank you all in advance!

 

[rhapdog]

To RAID or not to RAID! Remember, with Lara Croft, the answer is always RAID!

Instead of answering your question right out, I must say that education of RAID will be your best tool for deciding. Only you can decide what level of performance/reliability you are willing to accept.

I have been researching just that issue. I have been trying to balance the speed increase gained by RAID 0 with the safety and reliability of a good mirrored array. However, anything in the RAID world that does mirroring for data integrity will slow down your write speeds even over what a single drive does. That's what bothers me.

Even with a RAID5, if the problem is data corruption instead of a drive failure, which is more common, then your data is corrupted. You still have to do backups, regularly. Make sure you have an additional drive or 2 of the capacity to back up the entire RAID array.

RAID 5 will give the best balance of reliability + speed. RAID 0 is great for speed if you don't mind sacrificing data reliability. I don't recommend RAID 0 for anyone that does anything serious besides gaming.

You can build a RAID 5 array that is faster than many of the SSD drives on the market. You will be limited in speed by the throughput of the interface. I've heard people complain that putting 3 SSD drives in a RAID 0 didn't triple the speed, but that's because there isn't much room left for throughput on a SATA 6.0GB/s lane. Most of the speed is lost because of the interface.

What I do is the following, as I believe it gives me the best of all possible worlds:
1. SSD system drive and most common programs.
2. Data and program configuration files on RAID 5, with programs that are too large for the SSD. The RAID 5 I have setup is almost as fast as the SSD, but not quite. Should not be an issue to put everything on it. If I threw in more drives, it would be as fast or faster.
3. Portable eSATA drive same size as SSD to clone anytime I change OS files or update programs. This way if the SSD fails, I can swap it out for a new one and clone it back.
4. Portable eSATA drive same size as entire RAID array (2TB, for five 500GB drives, one is parity.) I use this 2TB to clone the RAID setup nightly so that it acts as a mirrored drive. That way, if I have a data corruption issue due to unexpected system shutdown or whatever, and the hard drives are still good, I can always go back to the previous nights mirrored clone.

It's a paranoid way of doing it, but if you have enough money to throw at a problem you can solve it, right? No... first you have to solve the problem, then spend your money wisely. If only the government could understand that.

If you just want data security, you might consider just getting 2 drives and cloning on a regular basis as a backup, or perhaps running them as a mirror (RAID1) if you don't mind the write delays. It is a less expensive way to get started. Just an idea.

 

[N3St]

Hi Rhapdog,

Thanks for a very informative answer Rhapdog, you just taught me more in 2 min. than Google could in 2 hours

After reading your reply I'm leaning towards a 2 x 1TB disk RAID 0 configuration in combination with an external USB 3.0 backup disk (that may run overnight). As far as I could figure out, I can use a simple software RAID (omitting the need for a separate controller), still keep my system fully backed up and gain some overall system speed through the RAID 0 configuration. However, I am also wondering what moved you to opt for this 5 disk RAID 5 configuration instead of just striping everything (since you back the full RAID array up as well). Also I am curious to what methods you use to backup the RAID array to a single disk and possibly image it back to the array in case you encountered a data inconsistency.

 

[rhapdog]

What prompted me to use the 5 disk array was a hard drive failure on a previous setup. Yes, I had a separate backup, but it is a pain to restore. With the RAID 5, I can just remove the bad drive and keep going, and when I insert a new drive, it will automatically fix itself. Also, another reason I went with the 5 disk setup is because I used to have a 2 disk setup in RAID 0, and someone gifted me 3 HDDs when they upgraded to 3 new 3TB drives. I can't resist a bargain, especially free.

I keep the clone mirror out of paranoia of non-hardware failure type failures. Like, in case I get a virus or something.

I use the Ultimate Boot CD at http://www.ultimatebootcd.com/index.html in order to boot into GParted (Linux distro), and then I use CloneZilla to do the work. This doesn't work, I don't believe, with a software raid. I have a hardware raid setup. And I can't clone "disks", I have to clone "partitions", otherwise, it would only clone a single disk stripe. I put the CD on a bootable USB stick to make loading faster.

It was a bit tricky for me to figure out the first time. I'm sure there are better ways to do it, like a dual boot to Linux to handle it. Perhaps there is a way to boot directly to Clonezilla or something else like it, and there is a lot of other cloning software. Find a good one that meets your needs. I use what I use because I never got around to researching other alternatives yet. I keep meaning to, and life keeps getting in the way.

 

[N3St]

Thanks again! Since I don't know if I can keep up cloning on a regular basis, I think a 3 disk RAID5 setup with a daily synchronisation of important files to an external drive or NAS may be the right solution for me. That way I will have increased speed and some redundancy because work will not be shut down upon failure of 1 disc. Since software synchronisation is easily automated, I will not actively have to concern myself with making sure that my files are backup up. The risk of course is that if I suffer from catastrophic system failure, I have to reinstall everything on new components, but I guess that is a risk I am willing to take. Thanks for the help Rhapdog!