RAID10

If I want a 1TB RAID10 how many drives would I need to create a robust,  no data loss and easy to maintain.  How do we need to set it up?

What happen when drive(s) failed?  What do we need to do to fix the problem?
tommym121Asked:
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rindiConnect With a Mentor Commented:
You need at least 4 500GB drives, create 2 mirrors with them, and then stripe those mirrors. You could also add an additional 500GB as a "Hot-Spare", if one of your drives fails, the how spare would take over automatically and rebuild the array, this reduces the chances of data corruption as you don't have to wait for the replacement drive to arrive and you can replace the bad one.

If 2 drives of the same mirror go bad, you loose your data, but if one drive on one mirror, and another of another mirror fails, you don't loose data.

When you replace remove the bad drive and put a good one in, then it depends on your RAID controller on what you need to do. Usually you have to open the RAID utility and then tell it what the new disk should be (if you are using a hot-spare, just mark it as the new hot-spare). Also, depending on the RAID controller and Disk Caddies, you often replace the disks while the server is up and running, but you'd have to make sure "Hot-Swapping" is supported on your server.
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andyalderCommented:
Hw fast do you want it to be? i.e. how many IOPS?

RAID does not protect you completely from data loss, you still need to backup, what happes if the system catches fire or a virus wipes the data?
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tommym121Author Commented:
Does it means if I want to have 2 TB,  I will need 1TB hard drive?  And If I only want 500GB, I will need 250GB drives instead.

Now does it make sense to have 6 drive so we can add parity for extra safety?
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andyalderCommented:
I'll ask you again (with the missing "o" this time), How fast do you want it to be? If you don't want speed then there's no benefit of RAID 10 over RAID 1 in which case you could use two larger disks mirrored in RAID 1.
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tommym121Author Commented:
My software vendor recommend me to use this configuration.  The software is to collect data and centralize it at the server.  The system log around 9G per day.  No sure if this is all the information you need to answer my question.

4x 500GB hard disks, with 2 extra as backup. Running RAID 10. 10,000 RPM.
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andyalderConnect With a Mentor Commented:
Assuming that logging is constant over 24 hour day then even if you are writing 512 bytes per record which is the smallest a disk can take then you need 18,000,000 I/Os per day, 208 IOPS. a 10K disk gives you about 120 IOPS so they're right, 4 * 10K disks in RAID 10 will do the job. You might want one more for a hot spare but two more is overkill, you've already got redundancy as each disk is mirrored to another one with RAID 10.
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tommym121Author Commented:
andyalder,

Would you recommend RAID5 over RAID10 for the same scenario?
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andyalderConnect With a Mentor Commented:
No, RAID 5 is poor for writes and has less redundancy than RAID 10. It does save in disk costs for capacity and the RAID 4 write penalty can be offset a bit by a decent RAID controller with battery backed cache but RAID 10 is still superior.
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tommym121Author Commented:
Thanks
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