Question regarding "Replace Disks with larger ones behavior"

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nissl
Posts: 25
youtube meble na wymiar Warszawa
Joined: Sat Jan 18, 2014 10:48 pm

Question regarding "Replace Disks with larger ones behavior"

Post by nissl »

Hi all,

I'm looking forward to replace my 4TB Hard Drives with 8TB or 10TB disks (not yet decided)
Currently I'm running the AS-606T with 6x4TB RAID5.

Now my question:
It sounds easy to replace the Disks with larger ones. But in the Manuals I found so far always all disks have been replaced.
Is there also the Option to replace only so much disks as needed to store the exisitng amount of Data.
Example:

Now the NAS is almost full with 17.5TB (of 18.03TB).
Lets assume I decide to buy the 8TB Disks. Would it be possible to replace the first four Disks and resync the RAID to them and remove the remaining 4TB Disks afterwards?

It would be good this function is implemented. Otherwise I'll have a problem. Due to the costs of the Disks i only want to replace the much as needed. To gain more Space i would add another one soon after the "migration" but then I'll still have 2 Bays free for the future.

Can someone help me with that? If this is not supported, which other options do i have then ?

Thanks and greetings

Dennis
MikeG.6.5
Posts: 917
Joined: Fri May 15, 2015 1:56 am

Re: Question regarding "Replace Disks with larger ones behavior"

Post by MikeG.6.5 »

What RAID level are the disks set up for? If you have the first 4 in RAID 5, then you can do them by themselves. And then follow up the other 2 as money/time permit. In order to increase the size of an array, regardless of the size originally, all of the disks of that array need to be the same physical size.

On the other hand, if all 6 disks are in a single RAID Array, then the only option is to do them all as the documentation says. One at a time until they are all swapped out, then increase the volume size only after all 6 have been synced.

This has to do with how a RAID array size is determined. Depending on the RAID level, the size is dictated by the smallest drive in the array. Data is stored in the same physical sectors across all of the disks in an array.

Think of it as a layer cake, if you will. You can't cut the cake layer that's the second down without cutting the top layer. And to actually serve the cake you need to make 2 cuts from the top to the bottom layers. (One cut for each side of the serving.) Each cut corresponds to the data of a file. It starts on the top layer, but goes through each layer until you hit the pan. Data is stored in an array in a similar manner. It starts on one disk, but then goes to the second in the same physical sector of the second disk, etc. until the end of the data. If one disk is smaller than the rest, it can't write to sectors of disk space that aren't there, as it doesn't physically have the sectors on the platter. So the size of the array (or the cake) is determine by the smallest disk in it.
nissl
Posts: 25
Joined: Sat Jan 18, 2014 10:48 pm

Re: Question regarding "Replace Disks with larger ones behavior"

Post by nissl »

Thanks for your reply

yes, i can confirm that. I opened a ticket for this case and the support staff replied almost the same.

So my option will be, save all the data from the Volume1 and delete it, then rebuild it on the new disks.
Unfortunately it said i will loose all my users, groups and off course shares of that volume.

But i guess there are config files which i can save somewhere to insert them after rebuild of volume1. right ?

Can someone point me to the most important config files and spare me a lot of time browsing the (little messed) file structure on the nas ?

Thanks and regards.
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orion
Posts: 3482
Joined: Wed May 29, 2013 11:09 am

Re: Question regarding "Replace Disks with larger ones behavior"

Post by orion »

I believe there are many configuration files, rather than just one. ADM web -> Backup & Restore -> System Settings -> Export Settings. That should be able to save your system settings. However, I guess that function is applied with the same system configuration. I'm not sure if it will restore RAID configuration (from 4 disks (new RAID configuration) to 6 disks (your original RAID)) when you import the settings. :(
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