Kelvin Paull

Should I partition a raid 5, or have multiple raid 5s?

5 posts in this topic

Hi everyone

I've have a question and I am wondering what is the best option for me.

background:

- I have 5x1tb drives which I am going make into a raid 5.

- I want to stay within the 2tb limit for partitions.

Should I make one large raid array of 4tb and then partition it into a minimum 2 volumes, or should I make 2 raid 5 arrays of 2tb each.

for references: when I had 4x750GB drives in my system, it between 1h:15m to 1h:30m to build a 1.5tb raid 5 array.

for the record, I am leaning toward smaller raid 5 arrays such as 2x2tb, or 2x1.5tb and 1x1tb. I want the arrays smaller so the rebuild times will be quicker.

Is the multiple raid 5 arrays a good way to go. Can anyone provide pros and cons for my current set up.

Thank in advance.

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The shorter "rebuild time" buys you nothing if you have two arrays sitting on top of the same 5 disks. If a disk goes and is replaced, both arrays will need to be rebuilt.

Meanwhile, if your OS / hardware has a 2TB drive limit, you *must* carve the disks into multiple arrays as you won't be able to access any sectors beyond 2TB on the array if you make one large array.

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The 2TB limit is partition table overall size, not per partition. What controller are you using? 3ware, and maybe others, allow you to carve off 2 TB chunks that show up as their own LUN.. Also, if your OS is modern enough, you can just use GPT partitioning which doesn't have the 2TB limit

Edited by compwizrd

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It sounds like he is using the onboard Intel Raid.

If this is true, that would be a big mistake. First off, Intel's Raid doesn't support "Carving". Second - read about all the problems people are having with onboard Intel Raid 5. Over at TomsHardware, there are a couple of long on-going threads discussing these problems. People have been experiencing major problems with large 2TB+ Raid arrays also. Another problem is using "Desktop" drives in a Raid array and the drives magically dropping out and then coming back which causes a rebuild. It sounds like you might have experienced something like this already due to your comment about Rebuild times. I won't go into it any further at the moment but I will suggest a good alternative.

The Highpoint 4320 8 port Sata/SAS PCI-E x8 Raid controller, which is on sale at Newegg for $290. It has the Intel IOP348 dual-core 1.2GHz processor which is one of the best Raid(XOR) processors. The card is normally $600 and nothing can touch its performance at its current price.

What OS are you using?

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Since the question hasn't been answered yet, and I'm wondering about the same thing. Can anybody give an answer:

Is it better to create multiple arrays or one array with multiple partitions?

(Using a RR2640 with 3x 1.5TB)

thx

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