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Raid 1 from a single drive

Software RAID information and help
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Raid 1 from a single drive


Post by nicolas1400 »

Is it posible using nas4free, to declare a single drive and start working with it, and later add a second identical drive for building a RAID1, without losing the data on the original drive?

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Re: Raid 1 from a single drive


Post by shakky4711 »


I have done it in the past one time by shell commands on a FreeBSD machine and it worked, but it is extrem risky, file system was UFS2.
Better way (but I would not do it likewise) is to create the mirror with two disks, then remove the second one. In this case you run a degraded mirror.

ZFS can do it out of the box by shell commands (not sure if it is possible by WebGUI).
When you have a pool named tank containing one disk called disk1 you can create the mirror with "zpool attach tank disk1 disk2".

google for "solaris zfs administration guide", it is a free available document from oracle and shows all zfs features and tips how to work with it.

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Re: Raid 1 from a single drive


Post by ku-gew »

Adding disks to a mirror is always possible. You can for example make a mirror with 2 disks and add a third disk (as mirror), so that you increase the performances for both random seeks and sequential transfers and, at the same time, improve the fault tolerance.
The same change 2->3 applies also to 1->2. The change is not risky, risky is only having a single drive in the beginning (drives fail often in the first three months and then only after years).
If you are aware of the risk of having a single drive in the beginning, go for it.
When you are ready, from the command line "man zfs" and "man zpool" and then, after reading everything, "zpool add _pool_ mirror _new_device_" (I think, check the syntax).
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