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My goals are simple: maximize data retention safety, and maximize read speeds. My first instinct is to do a a three drive software RAID 1. I have only used fakeraid RAID 1 in the past and it was terrible (would have led to data loss actually if it weren't for backups)

Would you say software raid 1 or a cheap actual hardware raid card? OS will be linux.

Could I start with a two drive raid 1 and add a third drive on the fly?

Can I hot swap?

Can I pull one of the drives and throw it into a new machine and be able to read all the data? I do not want a situation where I have a raid card fail and have to try and find the same chipset in order to read my data (which i am assuming can happen)

Please clarify any points on which it sounds like I have no idea what I am talking about, as I am admittedly inexperienced here. (My hardest lesson was fakeraid lol)

Thanks!

Edit: OS will be Windows 7 for one machine, Linux for another. Is three disk hardware RAID 1 possible?

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I think that for local storage, ZFS is probably your best bet. I'm not qualified to write that out as an answer, though. –  Basil Mar 20 '12 at 19:40
    
Which OS, hardware etc? –  Andrew Mar 21 '12 at 2:23
    
What do you think, software raid or a real raid card? Which one would give better read performance? –  cat pants Apr 26 '12 at 19:35

3 Answers 3

The best alternative with regards to speed and redundancy is a raid10. Plus it gives you more space than a raid1.

If you use mdadm on linux you can use a 3 disk raid10. See my question and answer here with regards to that: How to create a bootable redundant Debian system with a 3 or 4 (or more) disk software raid10?

In addition it may be worth your while to look into a good quality hardware raid controller to drive your raid10. I quite like the 3ware controllers LSI sells, but those may be out of your budget.

My experience with low budget raid controllers is that those tend to use some kind of softraid implementation so you're gaining nothing and may be at the mercy of bad implementations. In that case it's better to use the software alternative your OS provides, such as mdadm in Linux.

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Hardware RAID is preferred for data safety but even more important is to have a good offsite backup plan (also known as Business Continuity).

Adding a third drive to a RAID 1 is dependent on the controller. Hot swap is also dependent on the controller.

With hardware RAID you will need an identical RAID card in the other machine to be able to read the data but even then many controllers will require you to initialize the drive deleting all the data.

The bottom line is that you can go cheap but keep your resume updated.

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no, if you have 2 identical hardware controllers, they will usually recognize the configuration of the "foreign" drive when you move it. Just take care to "import foreign config" and not initialize the foreign drive. –  Olivier S Mar 20 '12 at 20:45
    
True for some but not all controllers. Just about everything depends on the controller which is why I said "many controllers" and not all controllers. –  murisonc Mar 20 '12 at 23:28

You can use a software raid 1 with three disks - but if that is not SCSI/SAS you will get a write-penalty for this.

With three disks a real hardware raid5 starts to makes sense (the more drives- the better).

With "real hardware" I am talking about a raid controller that does all the CRC-computing in hardware fast enough so you do not notice it.

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