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From: Baron Samedi on 25 Jan 2008 01:55
Hi,

I can't afford an external housing with built in RAID, so will
accept software based RAID.

I have an external housing, connected by USB, containing two identical
hard drives.

Can I make them appear as one, by using RAID 1 (mirror) in software?

If so, how?

Thanks in advance for any help.
From: Baron Samedi on 25 Jan 2008 02:04
On Jan 25, 2:55 pm, Baron Samedi <Papa.Legba....(a)gmail.com> wrote:
> Hi,
>
>   I can't afford an external housing with built in RAID, so will
> accept software based RAID.
>
> I have an external housing, connected by USB, containing two identical
> hard drives.
>
> Can I make them appear as one, by using RAID 1 (mirror) in software?
>
> If so, how?
>
> Thanks in advance for any help.

Errm, they are SATA, if taht makes any difference.
From: Anton Ertl on 25 Jan 2008 07:45
Baron Samedi <Papa.Legba.666(a)gmail.com> writes:
> I can't afford an external housing with built in RAID, so will
>accept software based RAID.
>
>I have an external housing, connected by USB, containing two identical
>hard drives.
>
>Can I make them appear as one, by using RAID 1 (mirror) in software?

If you see each drive as a separate device (which is probably the
case), then yes, you can.

>If so, how?

With mdadm, or with the installation software of your distribution.
You will typically partition the drives in the same fashion, and then
combine each pair of partitions into a RAID1.

Note that with this setup, performance won't be great, especially for
writes: On writes all the data has to go through the USB twice, and
the fastest transfer rates I have seen through USB are around 30MB/s.

- anton
--
M. Anton Ertl Some things have to be seen to be believed
anton(a)mips.complang.tuwien.ac.at Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html
From: Baron Samedi on 27 Jan 2008 21:12
On Jan 25, 8:45 pm, an...(a)mips.complang.tuwien.ac.at (Anton Ertl)
wrote:
> Baron Samedi <Papa.Legba....(a)gmail.com> writes:
> >  I can't afford an external housing with built in RAID, so will
> >accept software based RAID.
>
> >I have an external housing, connected by USB, containing two identical
> >hard drives.
>
> >Can I make them appear as one, by using RAID 1 (mirror) in software?
>
> If you see each drive as a separate device (which is probably the
> case), then yes, you can.
>
> >If so, how?
>
> With mdadm, or with the installation software of your distribution.
> You will typically partition the drives in the same fashion, and then
> combine each pair of partitions into a RAID1.
>
> Note that with this setup, performance won't be great, especially for
> writes: On writes all the data has to go through the USB twice, and
> the fastest transfer rates I have seen through USB are around 30MB/s.
>
> - anton
> --
> M. Anton Ertl                    Some things have to be seen to be believed
> an...(a)mips.complang.tuwien.ac.at Most things have to be believed to be seenhttp://www.complang.tuwien.ac.at/anton/home.html


Thanks for the info, that sounds like what I want.

I'm not too concerned about slow write, as this is mostly photos, with
the odd movie and maybe a little MP3. Wrtie is only once, intially,
it's not like they are data fiels that are regularly opened and
updated.
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