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I am going to lease a server and I have two options, SATA or SSD, I decided to save the money and go for the SATA option. But I do not need all that storage they are giving me! So I thought MAYBE I can setup RAID-0 to improve performance of my HDDs.

Since the server does not have a RAID controller I can only set up software RAID, I've had my experience with RAID on another machine with Windows installed! But I did not really notice any difference.

This server will have CentOS installed, so my question is, will I really gain any performance advantage for setting up SOFTWARE RAID-0 on a CentOS machine? Or is it not worth the efforts?

Thanks!

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RAID 0 is not really RAID in terms of redundancy. It is more of an anti-RAID. Here's the original RAID paper: cs.cmu.edu/~garth/RAIDpaper/Patterson88.pdf –  dmourati Jan 8 at 0:20
    
Yeah technically RAID-0 should be AID-0. Also, just did some testing on the latest MLC FusionIO cards and we used 1, 2 and 3 in various combinations on the same machine. RAID-0 with 2 drives came in second and RAID-0 with 3 drives was the fastest by quite a margin (30 to 40% faster at most db ops than any non-RAID-0 config). –  Scott Marlowe Jan 16 at 23:31

3 Answers 3

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Yes, you will gain performance.

Each harddisk has a limit of how many I/O operations per time it can perform. RAID0 basically distributes the I/O workload across two hard disks. Due to some over head in the RAID0 implementation you can't reach exactly 200% of the performance of one disk, but certainly significantly more than 100%.

An easy way to verfiy this is the hdparm utility with the parameters -t and -T. To see more details about the utility check man 8 hdparm.

The Kernel wiki has a nice Article regarding performance on software raids.

I do have to mention tough that a RAID0 basically doubles your risk of a downtime due to a broken hard disk, because if either of them breaks you are down.

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Thanks for your answer, the page you linked to was very helpful.And regarding downtime I will be using SSHfs for off-site backups so I think I will be alright –  AL-Kateb Jan 4 at 14:46
    
@AL-Kateb: Just to make sure: A backup is an extremely important and good thing, but it will not protect you from downtime due to broken disks - when a disk dies, your server will be down until it is replaced and you have restored the data from the backup. So you should think twice if you really need the performance benefit of a RAID0. –  Sven Jan 4 at 15:09
    
I got that thanks, I've never experienced any hard disks failure with this provider and since I will be have 1 GBPS on both servers and they are relatively close together, it will just be the matter of replacing the drive and copying over the data. I need RAID0 Cos hard disk I/O seems to always be the bottleneck in my setups, thanks for the clarification though. –  AL-Kateb Jan 4 at 16:04

You should use RAID-1 for your setup. Even if you don't noticed improvements for writes, you still get faster reads, as stripes can be read from both disks and you if one of your disks fail, you can just ask the provider to replace the broken disk and sync them.

Just because you haven't had a hard disk fail with a provider, doesn't mean you are safe. You will have a HDD failure at some point.

And to get the best performance, make sure your partitions are aligned and that you tell your filesystem to use the correct parameters for the stride/stripes (http://busybox.net/~aldot/mkfs_stride.html), otherwise you might not get the best performance.

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I would just like to remind everyone that RAID is not a backup method. Whether you have a RAID-0 or RAID-60 you should be making regular backups and replicating your database as well if your data matters. –  Scott Marlowe Jan 16 at 23:29

Yes sure, With raid 0 you will:

Enhance performance as blocks are striped. For both read and write operations.

You will not gain any redundancy with this raid.

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I understand this, but I was wondering if SOFTWARE RAID will have the same effect cos I tried it on my computer and set up software raid with Windows and there was no improvement –  AL-Kateb Jan 4 at 11:24
    
Will if you have created a single raid partition and started to copy files from or to it [speed will be duplicated if you are using 2 HDDs for that raid partions], you will notice the difference in speed, but will not see the difference in the other partions. –  MohyedeenN Jan 4 at 11:28

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