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Server raid questions!

Last response: in Storage
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August 26, 2011 8:01:42 PM

Hi,
I am planning on building a server that will have 3TB in a RAID 5.
I've built many computers although this will be my first server build.
The servers purpose is learning, web hosting, and computing.
I plan on running XenServer with at least 2 VMs consisting of Windows Server 2008 R2 and CentOS
I plan on using TrueCrypt for both windows and linux to encrypt all data.

• Never done RAID 5, only RAID 1... when doing RAID 5 will 3x 1TB HDDs show up as one 3TB partition?
• When I set up the VMs should each have its own partition in the RAID? Then each OS would handle encrypting its own partition?
• Should I opt for "shared storage" that can be accessed from any VM along with the VMs dedicated space?
• If I do have some form of shared storage what file system should I use for it... and how would I go about encrypting it so each VM can access it?
• Is a volume encrypted with a TrueCrypt algorithm readable from multiple OS?
• When I run out of space on the initial server and I have no more room for physical HDDs can I add additional storage as NAS?
• Will the above add on to my initial RAID 5 or will it be seperate?
• Is the above the best approach to adding additional storage?

Feedback to any or all of the above is appriciated!

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a c 415 G Storage
August 27, 2011 1:15:13 AM

Never done RAID 5, only RAID 1... when doing RAID 5 will 3x 1TB HDDs show up as one 3TB partition?

Three 1TB drives in RAID-5 will give you only 2TB of usable space.

If this is the only drive in the system then I'd advise against using RAID-5 because its very poor write performance will drag down the speed of all the other disk accesses in the system - this would be particularly bad in a VM environment where (I'm assuming) you'd have mulitple OSs trying to use the same slow RAID volume.
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August 27, 2011 3:40:02 AM

Then perhaps RAID 10 would be better? Although this would require 4 drives correct?
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August 27, 2011 3:41:06 AM

I suggest that your raid 5 array be a storage array, and not your system disk. This saves a LOT on monkeying around with drivers. Also, Raid 5 is (typically) not super fast.

The amount of space given over for the parity drive is a whole drive (your usable storage is n-1 (n= number of drives)). Therefore, if you have three disks you will lose the equivalent of one disk of space. If you really want 3TB I suggest doing it with (5) 650GB drives or (6) 500mb drives. This way, you'll have more storage space available and also benefit from faster reads and writes.

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August 27, 2011 4:15:10 AM

Ok so lets say I go with 5x 750GB HDDs in a RAID 5 to get 3TB. I would still need a separate drive for the VMs OS'.
Lets say I were to go with 128GB SSD for OS'... I wouldn't have to setup partitions for each VM would I or is that something you allocate when setting up the VM? Is 128GB split between a few VMs too small? If so I won't be able to get a SSD due to costs.
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