Russ,

Thank you VERY much for your detailed information about Raid0 and Raid1.
The machine in question is working as a mail server, perhaps that's why
the owner is inclined towards using Raid1, because he is getting 'smart
event alert' warning about imminent disk failure.

The hardware way of setting Raid is through BIOS setup? That's the way 
current Raid0 was set. I'll know more details tomorrow, when I'll be able 
to access that computer.

All the best,

Irena.

On Fri, 17 Feb 2006, Russ Poffenberger wrote:

> Hi Irena,
>
> While you didn't really give us enough information to answer this question
> completely, the most probable answer is no, there is no easy way to do this.
>
> RAID 0 refers to disks that are combined by striping the data across them in
> an interleaved fashion. This is mostly done for performance reasons, or
> could be to make the combined total of both disks look like one large disk.
> The downside of this type is that if either disk fails, you have likely
> corrupted all the files on both disks because any particular file's contents
> will be split among the RAID members.
>
> RAID 1 on the other hand is a mirror set, where the disks are copies of each
> other. This can be for improved read performance, but is more often for
> redundancy and robustness, since if one drive fails, the other has an exact
> copy, and the OS can "fail over" to the one working disk.
>
> The reason why the details of your setup is important is because there are
> different ways to achieve RAID. One is in software, but is not used much
> because of performance issues. The other is hardware, typically these days
> built-in to the disk controller itself. In fact, many motherboards now
> support RAID directly in their onboard chipsets and controllers. The
> difficulty with these is that the RAID management is done directly in the
> hardware and requires different layout and setup of the RAID tables on the
> disk. Since the hardware handles this, you cannot switch from one type to
> the other without losing your data. The other problem is that if your RAID 0
> set has files totalling more than the size of a single disk, then you can't
> fit the files on a RAID 1 set because your total space available is half
> that of the RAID 0 set.
>
> This gets even more problematic if the RAID set is also the boot volume.
> Probably the only way to convert would be to backup the whole RAID set to
> another medium, change the RAID type, re-partition, re-format, and restore
> the backup.
>
> The final question is why do you want to do this? Besides ending up with
> half as much disk space, there is usually not much need for RAID 1 except on
> high availability servers where loss of data or system downtime are
> unacceptable.
>
> Russ Poffenberger
> [log in to unmask]
>
>
> Hi Guys!
>
> We have 2 SATA disks configured as RAID 0. Can we easily change to RAID 1?
> If so, how?
>
> Thanks in advance for any pointers.
>
> Irena.
>
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