Jack,
Maybe a good idea to post the answer to the question I asked you offline for other potential users to see...
Good idea David! Here is the exchange:
In response to a question David asked me via email about how the DROBO can be formatted and partitioned, here was my answer:
DROBO formats itself as one large drive. In standard form it will show up as a 2TB volume REGARDLESS of how many or what size drives you place in it. If you place four 1TB drives in it thusly configured, it will show two volumes AFTER you exceed 2TB of data on it -- a 2 and a .8 -- but will spread your data across them automatically. IOW you do NOT have the ability to "partition" DROBO to your liking, for example two 1.4G volumes. You can however add any number of folders you want and let them expand until you run out of room. Next, using the DROBO software, you can format it to show as a 1, 2, 4, 8 or 16 TB drive. The advantage is you won't span multiple volumes, but the downside is it takes longer for DROBO to boot, about 1 minute per TB as formated, as it needs to check 4TB of data as opposed to 2. I chose the 4TB option since I plan on leaving it running most of the time anyway and wanted to see it only ever as one volume, so not too concerned about longer boot/check cycles. When/if I replace a 1TB drive with a 2TB drive, then even my format at 4TB will span across multiple volumes. This would require a re-format to 8 or 16TB, but of course all data would be lost on a reformat and need to be rebuilt -- again, another reason I chose the 4TB option at the outset...
On Jul 24, 2008, at 4:00 AM, David Kipper wrote:
This is NOT the way I thought this worked but should still work fine for me... at least I think it should. Let me explore this a bit further. Let's say I start with 2 x 1TB drives and 2x 500 GB drives (in a way this doesn't appear to be an optimal arrangement since the Drobo "reserves" space equal to the largest drive installed so you get less bang for the buck this way).
That is correct, DROBO is going to be most efficient when all drives are equal size, but really doesn't matter that much as you'll see in a minute.
Once I've run out of room I pull out one of the 500 GB drives and replace it with a 1 TB which should give me a true net increase in storage of 500 GB since the "reserved" portion is already maxed out at 1 TB. Have I got this part right ?
Precisely correct. Note that the amount of reserved space is not exactly equal to the largest drive, but close enough for our purposes on estimation.
Now I've run out of room again, substituted another 1 TB for the last 500 GB and run out of room once more.
Yes, and you get the next 500G of space, so you now have 4 @ 1TB drives and a total of 3 TB protected storage.
What happens now... Do I daisy chain more I TB drives in external boxes or substitute a 2 TB drive for one of the 1 TB (I didn't think there was such a thing as a 2 TB drive).
You can daisy-chain in another DROBO for sure, but there likely will be 2TB drives long before you need to do this, and you could pop out a 1 and start replacing them with 2's as your needs grow. The advantage of waiting until you need it, is the larger drives usually command the highest prices per gig of storage when first announced, but drop significantly after a few months. For example, just 6 months ago, 1TB drives were selling for just under $300 while 500G drives were just over $100 --- we would have been far better off using 4@500GB than 2@1TB from a price point of view. Now the 500G drives are around $90 and the 1TB's around $170, so pretty close per gig...
Also, if you need to reformat it at that point where the heck are you going to store the data you've got on your existing drives.
You only need to format the first time you plug it in with at least two drives installed. From there on it will automatically format the new drives you add or replace them.
Does it make any sense to format the Drobo as an 8 or 16TB drive at the get go. Like you I could care less about the boot up since it will likely be running all the time.
This is precisely why I chose 4TB, as I won't hit a full 4TB until I have 2@1TB plus 2@2TB. Replacing 1 of the 4 1TB drives with a single 2TB drive is unfortunately NOT going to get us much total storage gain -- back to the original formula, the total drive space minus your largest drive
So when we do finally swap in 2 @ 2TB drives (we'll have to do them one at a time and let DROBO build across the first before installing the second) we will have a true, single 4TB volume...
So our format issue will crop up as we add drives beyond that and there is no easy way to reformat once you've started a DROBO unless you have all your data backed up yet again off DROBO. I happen to since I keep redundant single drive copies of all my images stored offsite in case of fire or theft at my main office. However, at that point having data spread across 2 4TB volumes seems like a small issue -- the data is still there and visible, just maybe have to look in two places for it instead of one.
The problem with the boot times is DROBO needs 1 full minute for each TB as formatted. So if you start out formatting as 16TB, then every time you start DROBO after a shut down or power out, it would take 16 minutes to come online even if you only have 2TB of data on it... Hence I felt there was a good balance between volume size and boot times for me at the 4TB setting...
Cheers,