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Is it possible to have a machine (used for storage) with the following:

Lets say all the HDD's are 73GB SATA drives.

1 HDD for the OS. 2 HDD for the storage (RAID 5, hardware) 1 Hotswap HDD which will need to hold the same data as the 2 RAID drives.

Any help is appriciated.

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The hot swap drive doesn't need to "hold" the same data as the RAID drives, it needs to be available to replace one of the RAID drives if one should fail. –  joeqwerty Jan 7 '11 at 13:24
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2 Answers 2

up vote 4 down vote accepted

RAID 5 requires at least 3 disks. Another option might be to RAID 5 the first three disks and just partition the presented RAID disk so you have a small OS partition and the rest as storage. Then have the fourth drive as the hot spare.

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+1. Additionally, if it isn't windows you might use lvm on top of the raid partition to provide greater flexibility –  Michael Lowman Jan 7 '11 at 13:17
    
Thank you Niall, sounds like the best idea. +1 –  Kyle Hudson Jan 7 '11 at 13:34
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Why would you duplicate the data in the RAID array to a separate disk? That is what RAID is for.

Solution: Setup a 4 disk RAID 1 or RAID 10 solution, and install the OS on the array but on a separate partition. Also make sure you use a LVM for features like instant snapshots of your disk.

RAID 1 is a straight mirroring of your drives and duplicates all information across the array. You need a minimum of two disks and you must add disks in groups of two. Total capacity 146 GB. In this configuration you can handle from one to two disks failing without data loss.

RAID 10 combines mirroring with striping and gives you the same space as RAID 1 with the benefit of increased read and write speeds. However you need a minimum of 4 disks to set it up. Furthermore, you must add disks in groups of two. Total capacity 146 GB. In this configuration you can handle from one to two disks failing without data loss.

RAID 5 is slow for writes, and most of the time not worth the trouble in server environments, but if you want to squeeze some more space out of your drives, then you can setup a 4 disk RAID 5 solution. Here 3 disks would be used for data, so you would have a total capacity of 219 GB. You can handle only 1 disk failing.

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