Using DNS323,ALT-F,RAID5, with an external JBOD box?

[Gaiko]

Hi João!

Its been awhile since I have posted but honestly its because everything has been running great! (thanks again for helping me get past the “2tb barrier”). Nothing has changed in terms of everything running smoothly, but I am starting to run out of space and a friend gave me a JBODs case (Addonics) that he was tired of which gave me a possible idea. This box has no bells or whistles, its supposed to plug in via esata but that doesn’t work so my friend got a esata2usb converter so that works so when its plugged in it just shows up as 4 separate disks, and you can use it as such (no network hook up, no RAID goodness, nothing more). What I was thinking/hoping, is that maybe, possibly, I could hook this up to my DNS-323 with ALT-F set it up for RAID5 (of course with all the same size/model/etc drives) and have it run as a nice big 6drive RAID5 box!

In my head this all sounds good in theory, but theory is one thing so I wanted to check on the forum to see if there are any (very likely) caveats that I am not considering here. Any thoughts (sobering or not) would be appreciated before I start tinkering etc.

Thanks in advance!

[Gaiko]

So it should work ok? hopefully? I am a bit more confident about plugging in just one additional ext drive but plugging in a device that is a bunch of additional drives is a slightly different thing hence my hoping to get some feedback about the idea.

[João Cardoso]

On Saturday, January 4, 2014 5:22:07 PM UTC, Gaiko wrote:

So it should work ok? hopefully? I am a bit more confident about plugging in just one additional ext drive but plugging in a device that is a bunch of additional drives is a slightly different thing hence my hoping to get some feedback about the idea.

On Sunday, December 29, 2013 3:13:32 PM UTC+4, Gaiko wrote:

Hi João!

Its been awhile since I have posted but honestly its because everything has been running great! (thanks again for helping me get past the “2tb barrier”). Nothing has changed in terms of everything running smoothly, but I am starting to run out of space and a friend gave me a JBODs case (Addonics) that he was tired of which gave me a possible idea. This box has no bells or whistles, its supposed to plug in via esata but that doesn’t work so my friend got a esata2usb converter so that works so when its plugged in it just shows up as 4 separate disks, and you can use it as such (no network hook up, no RAID goodness, nothing more). What I was thinking/hoping, is that maybe, possibly, I could hook this up to my DNS-323 with ALT-F set it up for RAID5 (of course with all the same size/model/etc drives) and have it run as a nice big 6drive RAID5 box!

If you have more than one USB disk/pen attached, the Disk Wizard will tell you:

For performance reasons you should have no more than one external USB disk.

If you have plugged a usb pen, eject and remove it and retry again

If all you want is capacity, In theory it should work, but you have to use the command line to setup the RAID.

But with more than one disk sharing the USB channel, performance will be lousy.

RAID5 works like RAID0, making simultaneous parallel access to all present disks, so the USB single link will be the limiting factor; in addition, RAID5 computes and spread redundancy data through all disks, so it will be even worse.

I wouldn't recommend it.

A simpler approach would be to use JBOD, but I don't recommend JBOD either, as if any single disk fails all your data will be put at risk (the remaining data is still there, but it is extremely difficult to access).

LVM is also a possibility, but it is even difficult to manager then RAID, specially in the event of disk failure.

The most manageable approach for normal users would be to have several "simple" filesystems, each one on one disk, and have a set of symbolic links to each filesystem. As simultaneous access to several disks through the USB is not likely to happen often (in a home user environment), performance will not suffer, and the only maintenance task to be done when a fs is near full will be to move data around filesystems. Careful initial planning/guessing/forecasting of each fs contents is a must.

This the way how sysadmins work in the early days ;-)

No free lunch :-(

[Gaiko]

Damn! :)

Well that is exactly what i needed to know... in theory it would work, but in practice it just wouldn't be usable. I was getting ready to prep (move some data around, format some drives etc) which would have taken me quite awhile (3tb drives) so thanks so much from saving me! And now I can say I am a wee bit wiser in the ways of RAID5 and Alt-F.

Cheers!