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Forum Discussion
WD Compatibility
Two questions: 1. I have two WD Elements and one WD My Book. I did a brief search for compatibile drives with the 104 and only came up with about three for WD. Is that right or was I looking i...
LDG wrote:
Let's say I buy a 2 bay disk less NAS and then a 1 tb to put in it. Once that is used up and I buy the second drive, will I have to format the first when adding the second?
There are two basic scenarios, depending on whether you are using jbod or xraid. Either way the NAS formats the drives.
With jbod, the simplest thing to do when the disk is full is to add a second disk (which would be its own volume). After that second disk becomes full, you'd need to get a larger one, destroy the first volume, remove the drive, and install the new larger disk. All data on the volume is lost, so you need to restore it from a backup,
With xraid, you actually want to start with 2 disks (say 2 x 1 TB). When you need to expand, you buy two larger replacements (say 2x4TB). First you'd insert the first 4 TB drive (with the NAS running). After the volume resyncs, you'd replace insert the second 4 TB drive (again with the NAS running). The NAS will then expand the volume to the larger size. There is no loss of data.
StephenB wrote:
LDG wrote:
Let's say I buy a 2 bay disk less NAS and then a 1 tb to put in it. Once that is used up and I buy the second drive, will I have to format the first when adding the second?There are two basic scenarios, depending on whether you are using jbod or xraid. Either way the NAS formats the drives.
With jbod, the simplest thing to do when the disk is full is to add a second disk (which would be its own volume). After that second disk becomes full, you'd need to get a larger one, destroy the first volume, remove the drive, and install the new larger disk. All data on the volume is lost, so you need to restore it from a backup,
With xraid, you actually want to start with 2 disks (say 2 x 1 TB). When you need to expand, you buy two larger replacements (say 2x4TB). First you'd insert the first 4 TB drive (with the NAS running). After the volume resyncs, you'd replace insert the second 4 TB drive (again with the NAS running). The NAS will then expand the volume to the larger size. There is no loss of data.
Xraid sounds much better...pretty much what I do anyway, actually. The downside is finding a way to keep the the first disks connected. I simply like having constant access to everything. Xraid allows for expansion the way I would like it to, but then I still have two disks that I'd like to continue to be accessible.
LDG wrote:
Xraid sounds much better...pretty much what I do anyway, actually. The downside is finding a way to keep the the first disks connected. I simply like having constant access to everything. Xraid allows for expansion the way I would like it to, but then I still have two disks that I'd like to continue to be accessible.
There might be still be some confusion here on what RAID actually does. XRAID creates a single volume (think of it as a "virtual disk") from the physical disks you have installed. By default the NAS calls this volume "data".
All your data is on this virtual disk, and you expand it by replacing the physical disks with larger sizes. All the data remains accessible when you expand - nothing is destroyed (unless something goes wrong).
Also, if a single disk in the volume fails, the volume is "degraded". But you still have all your data available. You pop in a new disk (either the same size, or matching the size of the largest disk in the array), and the redundancy is restored.
This doesn't keep your data completely safe (so you still need a backup). But it does keep everything available through routine disk replacements.
So with XRAID it actually doesn't make sense to say "I still have two disks that I'd like to continue to be accessible.", since the disks are all combined into the virtual disk.
StephenB wrote:
LDG wrote:Xraid sounds much better...pretty much what I do anyway, actually. The downside is finding a way to keep the the first disks connected. I simply like having constant access to everything. Xraid allows for expansion the way I would like it to, but then I still have two disks that I'd like to continue to be accessible.
There might be still be some confusion here on what RAID actually does. XRAID creates a single volume (think of it as a "virtual disk") from the physical disks you have installed. By default the NAS calls this volume "data".
All your data is on this virtual disk, and you expand it by replacing the physical disks with larger sizes. All the data remains accessible when you expand - nothing is destroyed (unless something goes wrong).
Also, if a single disk in the volume fails, the volume is "degraded". But you still have all your data available. You pop in a new disk (either the same size, or matching the size of the largest disk in the array), and the redundancy is restored.
This doesn't keep your data completely safe (so you still need a backup). But it does keep everything available through routine disk replacements.
So with XRAID it actually doesn't make sense to say "I still have two disks that I'd like to continue to be accessible.", since the disks are all combined into the virtual disk.
So if Drive A and B are in there and full, I can take them out and put same size or larger C and D drives in. Does the data from A and B stay on the virtual disk while I can add to C and D? Or do C and D need to be larger to accomodate the virtual data? Would the physical drives then act as back up?
I feel like I've drawn a false conclusion that a NAS can support virtual data itself, but that would mean they have their own internal storage and I didn't think diskless ones did.
You're right! I am confused! (maybe)
The "virtual disk" is built on top of the physical disks - so that all the storage is still on the physical disks.
For example, if you have four 3 TB disks installed, you have 12 TB of total storage. The NAS will create a 9 TB virtual disk. The remaining 3 TB is used to create redundancy - allowing all the data to saved on the 9 TB virtual disk to remain available even if one of the 3 TB disks fails or is removed.
This virtual disk looks like a single 9 TB drive to you. Also, your data is spread across all 4 physical disks. For instance, if you have a 4 GB movie, part of it is on disk 1, part on disk 2, etc. It still is one file, but it is saved across all the disks.
LDG wrote:
So if Drive A and B are in there and full, I can take them out and put same size or larger C and D drives in.
Again, it is meaningless to say Drive A is full. The virtual disk volume is what becomes full. The files are spread across all the physical drives.
When it does get full, you can replace the physical drives with larger ones (one at a time). So if you changed two of the 3 TB drives with 6 TB drives, the NAS would expand the virtual disk from 9 TB to 12 TB. The space needed for redundancy would also grow - in this example from 3 TB to 6 TB. The virtual disk then looks like a single 12 TB drive to you, with no data loss.
The rule for capacity is that volume size is the sum of all the disks minus the largest disk. The amount needed for redundancy is equal to the largest disk.
When you replace a physical disk, you either use a disk of the same size as the one you are removing, or you add a disk that is >= the largest disk in the array.
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