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


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#1 Kelvin Paull

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Posted 28 April 2009 - 06:00 PM

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.

#2 geshel

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Posted 28 April 2009 - 10:04 PM

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.

#3 compwizrd

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Posted 29 April 2009 - 12:20 PM

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, 29 April 2009 - 12:20 PM.

#4 **Special K**

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Posted 02 May 2009 - 03:38 PM

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?

#5 knirfie

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Posted 24 July 2009 - 05:53 PM

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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