# Seagate eSATA drives as raid

## cynric

I'm looking at purchasing two  Seagate ST3500601XS-RK 500GB eSATA drives. These come with PCI cards to provide eSATA ports. The system I plan on attaching these to is a fully functioning, non-RAID, Gentoo x86 box. I do not wish to have the whole system RAID, just these two new drives as RAID-1 for the mirroring capabilities and not performance. I assume that this array would be built with standard mdadm commands such as those found at Wiki - HOWTO Migrate To RAID or similiar RAID tutorials ignoring steps that involve bootloaders, installation, partitions, etc.

Assuming that that is as easy as it sounds, the only real question I have is are there any additional drivers needed specific to the PCI -> eSATA card? Any other comments regarding my setup are welcome.

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## thesheff17

well I would put in the gentoo min cd and type in lspci.  This will tell you what type of chip is on the sata controller.  Many times generic sata controllers have a good chip on it.  You may already know this but it may help some.  If lspci sees the controller then you can compile the driver as a module into the kernel.  Then you don't have to re-create the whole kernel.  

If you don't see it under lspci you may have to "modprobe driver"  Hope this helps.

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## thesheff17

actually looking at the drive more....doesn't it conect through usb? It is an external drive. Then you would just have to compile in usb support for gentoo.

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## cynric

Thanks for the reply. I don't actually have the drives yet so popping in the card for a quick lspci scan isn't possible. I'm assuming that it should "Just Work" as long as the PCI bus and regular SATA are functioning. However, there doesn't seem to be much online (so far, I've only done a cursory glance) about eSATA and linux -- this could be because things simply work or frustrated users haven't vocalized their problems.

As for it being USB, the particular drive I'm looking at doesn't appear to be from my understanding. eSATA is the interface (PCI card with two SATA ports on it). Most other drives are USB or Firewire though.

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## thesheff17

well I see you like newegg as do I.  I bought all promise sata controller cards and I know they work with linux.

http://www.newegg.com/Product/Product.aspx?Item=N82E16816102062

This one is a great example.  This one does not have hardware raid but running mdadm works like a charm.  It may be cheaper to buy this card and buy just normal sata drives.  This is also sata 2 which will help with speed.

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## cynric

Sounds good. Now I just need to familiarize myself with mdadm and ensure this is the way I want to go. Thanks for the confirmation on the controller cards.

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## thesheff17

Have used this how to about 1,000 times.  Works like a charm

http://gentoo-wiki.com/HOWTO_Gentoo_Install_on_Software_RAID

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## cynric

That guide seems to be comprehensive. I just wonder if there is anything in particular to watch out for when attaching a raid array to a non-raid system. Nothing seems to stand out to me and I'm sure going through the process will be enlightening, but it's always nice to have any "heads-up" people may have.

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## thesheff17

oh I didn't know you are moving from a non raid to a raid.  I would suggest this guide.  Haven't used it but seems like it should work.

http://gentoo-wiki.com/HOWTO_Migrate_To_RAID

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## paulisdead

One of the key things you might want to research is whether or not the controller supports hotplug under Linux.  eSata is just frickin cool, but so much more useful with hotplug.  I have to reboot to get Linux to detect a sata drive I plug in on my eSata ports.  It's very sweet to have full transfer speeds of an internal drive outside of your box.  If you intend to be unplugging the drives, and taking them somewhere else (which would be the point of external drives, unless your case can't fit them) it would be quite a hassle to reboot every single time.  I'm not sure how mdadm would react to moving the drives around like that though, so that might be a problem, and I'd be curious to know exactly what happens when you try to unplug the drives on a hotplug controller using mdadm.

Since you're not transferring the whole system to RAID, it's quite easy to get going too.  It's pretty much the whole scenario I had when I started using RAID software RAID on my home file server, an OS drive and seperate RAIDed storage for your files.  Just follow the wiki to get it setup.

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## cynric

I appreciate your input; both thesheff17 and paulisdead.

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