eSATA 2.5" Mobile Raid Enclosure Questions

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bnew019
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Joined: Mon Oct 15, 2012 11:15 am
by bnew019 » Mon Oct 15, 2012 11:39 am
Hello,

I have just purchased a eSATA 2.5" Mobile Raid Enclosure and have installed two 1TB Samsung drives configured in Safe50 mode. I have set up 3 partitions within RAID1, and set the rest as one partition. I have the enclosure connected by USB to my Raspberry Pi device which is running Raspbian, a form of Debian Linux.

This is so far working great and data writing and reading has no problems.

But I have two questions that I need help with:

1. How can I check that RAID1 is working correctly?
I disconnected the enclosure and removed one drive, and then connected the enclosure to my laptop. The partitions within RAID1 all mounted correctly and I could open a file. Of course the partition from the BIG configuration did not show up, but that was as I expected. So far so good, RAID looked like it was working correctly. However, I inserted the drive back into the enclosure, and then removed the second drive. Now the laptop did not recognise the drive and wanted to format it. If RAID was working correctly should I have been able to see the partitions mounted when I connected the enclosure? How can I ensure that if HDD1 fails from the RAID then HDD2 will be able to successfully rebuild the cluster if I insert another drive?

2. The drives in the enclosure are constantly spinning, can I stop them spinning if the disks are not accessed?
The drives start spinning as soon as they are connected to the power source, even if not connected at all to a computer. From Raspberry Pi, I have tried several Linux commands including hdparm, hd-idle but none seem able to stop the drives from spinning. I am looking to have the Raspberry Pi always on so that I can use it as a backup file server at home (hence why I wanted RAID), so it would be great to stop the drives spinning when not in use to save power and heat. Is there any way that I am able to do this with the enclosure?


Thanks a lot in advance for your help.

I must say that my first impression of the enclosure have been very good, and I did a lot of research into similar products online before purchasing this one. But I could not find something that did exactly what I required like this enclosure has done so far.

 

LINDY Shippers
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Joined: Wed Mar 17, 2010 1:32 pm
 
by LINDY Shippers » Mon Oct 15, 2012 12:21 pm
Hello,

1. We do not recommend RAID 1 for complete data backup, this would not give 100% protection - http://www.vantagetech.com/faq/raid-1-recovery-faq.html

Many people mistakenly assume that they are totally protected against data loss with a RAID 1 volume, but nothing could be further from the truth. A RAID 1 volume provides a measure of protection against data loss, but it does not eliminate the need for regular backup of critical data.

I'm afraid you wouldn't know the damage until its done, then and only then would you find out if its going to rebuild. I would also not recommend removing disks from the array as this could cause problems.

2. The driver has no support for spinning the drives down I'm afraid. The only way to power down the drives is a physical power off.

Best Regards
Chris

 

bnew019
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Joined: Mon Oct 15, 2012 11:15 am
by bnew019 » Mon Oct 15, 2012 3:18 pm
Thanks for the response Chris,

For point 1 I took the opportunity to test out the RAID before I really start using it to regularly back up data. Once I have started to back up everything that is critical, I will not be touching the drives again! I am a little confused on this though as I thought that the point of RAID1 was that the exact same data was written to both disks. So in this case because HDD1 was successfully mounted to the laptop, I expected that also HDD2 would also mount. The fact that it doesn't makes me worry that the RAID is not working 100% ie if HDD1 were to fail I worry that HDD2 would not have the full information to restore. Is there some way to check this? If RAID1 is not recommended for complete data backup, then what is the recommended method?

For point 2 are you able to provide any details of which drivers are used for the enclosure? Perhaps there may be some updates for them that might allow this in the future?


Thanks

 

LINDY Shippers
LINDY Staff
Posts: 655
Joined: Wed Mar 17, 2010 1:32 pm
 
by LINDY Shippers » Mon Oct 15, 2012 4:00 pm
The chipset is a Silicon Image I5744

I'm no RAID expert this is only what I've done before / heard - http://en.wikipedia.org/wiki/Standard_RAID_levels

The problem with RAID 1 (and RAID in general) is that if you have a file system error this will also be copied to the other disks. RAID 5 is very popular among server storage configurations. Even these RAID 5 arrays get backed up to another storage device. (I've even seen a RAID 5 fail and take all the data with it)

RAID 1 Its not designed to be 'pullable', disks cannot be used independant and then put back in an array, I'm surprised you're even getting one disk to show the data. If a disk fails it should be able to be rebuilt when a new one is inserted.

To get the array to rebuild you would have to create a problem with one of the disks but I'm not sure how you would go about that.

I hope this helps.

Chris
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