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Recently bought a server with 16 1TB disks. We're going to use this for a backup to disk solution.

Is there any reason why I'd want to partition the array in any specific manner? I was basically just going to RAID5 the entire thing and possibly just carve one partition for the OS (60-80GB) and leave the rest for backup storage.
However, I couldn't think of a great reason to create a separate partition, and so just wanted a little input.

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What kind of performance implications would RAID6 have on a 16 disk array? Also, How can you get windows to properly recognize the entire array rather than it splitting the array into unallocated disks. – Untalented Dec 30 '11 at 6:24
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I'm not quite sure if you're asking whether you should partition the OS separate from the backups, or if you're asking if you should partition the backups itself into smaller chunks.

First, I would highly recommend separating the OS from the backups. What if the OS got corrupted and you had to restore? That would be a pain for your backups. Also, (assuming you're using Linux) you can mount your backups with no "no suid" for added security, etc...

Secondly, how are the backups going to be performed? What will the file tree look like? Will everything be stored in 1 huge flat directory, or will there be sub directories? This will help determine your partition structure.

Third, have you considered a RAID 6 instead of a RAID 5? If you're going for backups (and performance isn't an issue), then this might be a better way to go. A RAID 6...

extends RAID 5 by adding an additional parity block; thus it uses block-level striping with two parity blocks distributed across all member disks. (Wikipedia)

It provides the added protection of allowing 2 drives to fail, instead of 1, during a drive rebuild.

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I appreciate the response. I was originally talking about the partitioning of the OS volume and whether to separate that from the backups. I see what you mean and it's probably a good idea to do this for the reasons you stated (ie. OS corruption). The backups will be in separate folders based on which server it is. In regards to RAID6, what's the benefit/downside to this vs. create a hot spare? – Untalented Dec 28 '11 at 14:10
Well, I'm not VERY familiar with RAID 6, but from what I understand, your performance will decline a little bit while your effective storage space will remain the same AND you can handle two points of failure and not one. On the other hand, if you had a RAID 5 with a hotspare, you would still only have 1 point of failure. If a 2nd drive were to die while the hotspare was being built, you'd be toast. This is a backup server, so I'm guessing redundancy, and not performance, is your primary concern. Heck, you could even consider a RAID 6 with a hot spare. – David W Dec 28 '11 at 17:53
I appreciate the response. Will consider this when I begin working on it tomorrow. I'll look into the performance aspect a bit further. – Untalented Dec 28 '11 at 22:21
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raid 5 is definitely not the way to go if you have 16 drives, as the rebuild times will be measured in the days, and any other failure during that time will result in total data loss. Although backups arnt usually mission critical, when you go days without backups due to the size of the array refilling, it can be. Raid 6 is raid 5 but can sustain 2 drive failures, but you have 1 less drive worth of space. I'm also building a 16 drive raid system currently (but with 2tb drives), and i went for raid 5+1, two raid 5 sets that mirror each other. – Sirex Dec 30 '11 at 8:48
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Performance hit will depend on the controller and workload - if you have time I would quickly set up a copy of windows or linux as you prefer and run some benchmarks to see if it acceptable in RAID 6. If it acceptable, so what if you can run faster but riskier?

Definitely keep your data and os seperate - if you ever wish to wipe the OS and start again it will make your life infinitely easier.

Also I was mentioning on another question - if your machine has EFI bios and can boot from a GPT partition, you could have one giant RAID with seperate partitions as using MBR rather than GPT limits you to 2Tb.

If it hasn't got EFI then you would need to create two raids - one (I would suggest 2 drive/RAID1) MBR partition for the OS and the rest as RAID6 GPT parition.

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This is very helpful! Is there an easy way to determine if the BIOS is EFI? What's a decent utility that I can boot to and create the GPT volumes or should I be able to do this from the Windows disk if the bios supports it? – Untalented Dec 30 '11 at 14:23
I haven't had much experience with EFI - google or HP support or documentation from HP website should be able to help you, or provide a model number and I will see what I can do. Here's a MS KB article on creating a GPT volume support.microsoft.com/kb/297800 – Robin Gill Dec 30 '11 at 20:06
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