What RAID to use for my home server?

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RAID for home use

I am setting up a home server to stream media to and I am unsure about what RAID to go for. Either 5, 6 or 10?

Leaning towards RAID 6 due to fault tolerance of 2 drives.

However, if one drive fails, does my hot swap drive need to be the exact same as the other drives in the array? E.g. does it have to be the Seagate 3th 7200rpm drive? or can it be any 3th 7200rpm drive? or any 3td drive at that?

UPDATE

I thought RAID 5/6 would be beneficial to me as it would ensure that my movies are retrievable after a disk failure. But the answers and links provided show that more disks could crash when rebuilding.

With RAID 10, what if a file becomes corrupt on one disk, will it be mirrored to the same section on the mirrored disk, resulting in the loss of all data on that disk?

One person asked why i needed a RAID, but im not too sure what my other options are? Even if i just make a back up of my expadning movie collection, what is preventing me from losing the backup if the disks the backup is on crash/become corrupt?

Thanks for all of your help!

user1139093

Posted 2012-12-16T23:09:57.057

Reputation: 3

Question was closed 2012-12-17T12:03:01.453

1Maybe you should explain why you feel you need RAID at all. Bad ant problem? – Daniel R Hicks – 2012-12-16T23:12:07.260

With RAID 10, if one drive become corrup then that half of the array will be dropped. Nothing will be synced. --- Say you have two stripes on a mirror (Drive1-Drive2) as a stripe, presenting itself as disk12, and (Drive3-Drive4) in a stripe presenting itself as disk34. With then a mirror over D12 and D34. Say drive 2 fails, then stripe 12 drops. The mirror will go to degraded and nothing will be written to virtual disk 12 and thus nothing to D1 or D2 – Hennes – 2012-12-17T00:05:43.687

Answers

1

The RAID level used should be selected based on the usage of the array.

This post on our sister site Serverfault explains it nicely, but to summarise:

For streaming large files (reading from the array), RAID 5 and 6 will work fine. Both continue to work in case of a drive failure (1 in case of RAID5, 2 in case of RAID 6).

For more performance, go for RAID 10.

In both cases you still need a backup. Both because you do not want to rebuild a large RAID array after failure (that takes ages and you have to hope a second drive does not fail during the rebuild), and because a file deleted or corrupted on RAID is lost as even if you can read that corrupted file. And human do tend to delete the wrong files on accident.

However, if one drive fails, does my hot swap drive need to be the exact same as the other drives in the array?

No. Any drive of equal or large size should do.

Note that larger drives tend to get rounded up to nice marketing values. Do not assume that a drive with the same value in a shopping basket is equally large. Should a drive fail, please do research how large it is and make sure the replacement is not smaller.

A few more things do consider:

  1. RAID is not backup. Fire, theft, lightning strikes etc will still kill all your data. Even with RAID, make sure you have an off-site backup. RAID just makes sure you do not loose data if a drive fails. Not in other situations
  2. Moving to RAID via a hardware RAID card introduces a new point of failure. YOu can withstand a drive failure, but a HW card still means you loose access to your data until the card is replaced.
  3. Same with Intel fake RAID (unless you have a similar motherboard).
  4. If you do not access the data on your desktop, consider a NAS. A RAID set up in your desktop will be much faster, but a NAS allows you to access stuff when the desktop is turned off.

Hennes

Posted 2012-12-16T23:09:57.057

Reputation: 60 739

Thanks for the answers Hennes! I'm not too sure what would be best for my situation. All i want to be able to do is to ensure that my movies (that i add to everyday) are protected/retrievable after disk failure. Im not sure if i need some form of RAID or just a backup solution? – user1139093 – 2012-12-16T23:53:12.870

You can use both. For that combine RAID5 with a backup. If a drive fails then make an incremental backup (only the files which have changed since the last backup), replace the broken drive, destroy and rebuild the array, using the data on the backup. No long waits for array rebuilds. No data lost and a backup somewhere else. – Hennes – 2012-12-16T23:59:09.613

Thanks again for the help. But if i destroy the array wont i be destroying the location of my backup? or would be backup be stored in a different location? – user1139093 – 2012-12-17T00:03:32.213

A backup should always be stored elsewhere. Preferably not even in the same house. – Hennes – 2012-12-17T00:06:55.763

exactly. A good setup is (say) 3x1TB drives in RAID 5 making a 2TB volume, and then 2 2TB usb drives, one to be kept at home, and one to be kept at work, to backup to alternatively. Keep those encrypted, (and ideally, have three of them to avoid any moment when all drives are in your house in case of fire). – Sirex – 2012-12-17T00:20:32.317

Ahh i understand now! However I am more concerned with disk failure as opposed to file corruption, so would RAID 10 be more suitable? Or if a disk fails do i still run the risk of other disks failing whilst the array is being rebuilt? – user1139093 – 2012-12-17T00:51:17.490

You always run the risk of another disk failing. The chance that that happens at the same time is relative small, but not zero. However during a rebuild you are stressing the remaining drives of the array. If you have 4 drives, bought at the same time (and fabricated in the same batch) and one fails then the remaing three are statistically more likely to fail roughly at the same time. Add a nice stressful array rebuild to that as well as large drives (and thus a long stressful array rebuild) and the chance gets a bit bigger than I am comfortably with. – Hennes – 2012-12-17T01:01:57.750

Note that the risk of that is still small. But if you go all the way to building an array then your data is probably important to you. That does not combine with ignoring risks to that data. – Hennes – 2012-12-17T01:03:29.437

@user1139093 -- I'd be more concerned with file corruption. I'd guess it's about 10x more likely than drive failure. – Daniel R Hicks – 2012-12-17T01:07:47.860

It might be more likely than disk failure, but it wont take me 5 minutes to redownload a corrupted movie file. however it would take me ages to redownload a whole HDD worth of movies! – user1139093 – 2012-12-17T09:36:45.077

What about if i ignored raid altogether and had one disk storing my movies which was backed up to another disk? – user1139093 – 2012-12-17T09:38:41.040

Where will you store that other disk? As long as it is the same location you have the same vulnerability to fire, theft etc. – Hennes – 2012-12-17T10:21:35.453

Consider this: Use RAID only in these three cases: 1) Maximum speed regardless of risk (striping). 2) You want to play with RAID and learn from it. 3) The most common case: You want something which will keep a server up and running till 5PM, even if a disk failed. At 5PM everybody goes home from work and you fix the corporate server. --- Neither of these replaces backups. – Hennes – 2012-12-17T10:23:48.980

Asked: 2012-12-16T23:09:57.057

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Active: 2012-12-17T00:01:06.107