The Drobo (and the expandable RAID setups on other systems) do RAID across drive partitions. If you add/replace a new larger disk, the extra space sits there going to waste initially. But if you add/replace two disks with larger capacities, it will create a second RAID across the leftover space, and usually use LVM or similar to add it into the overall storage pool.

The Drobo's have a bad habit of never reoptimizing, so after many drive swapouts and upgrades, the units can become very slow. I believe the ReadyNAS XRaid, and similar tech from other providers is a little better about this, but I'm not certain of the details under the hood.

The EVA rack sized storage boxes I worked with at HP would use idle time to reoptimize the data. Both for performance, and for maximum redundancy, factoring in the physical layout of the independent disk shelves, and even different racks.

Just F all YI: Western Digital has just announced their new 4TB drives. These drives are 'enterprise class' and come with an appropriate price tag (about 450 euro per drive!). The drives are 7200rpm though, and come with a 5 year warranty. These are not the usual Green Drives range. As far as I can see, these drives use 800GB platters. So this means 5 platters in a HD, which is too much for the drives to still be called 'Green' because they'll probably consume a relative large amont of power.

So WD 4TB drives are finally here. After Hitachi (which is now also WD in a way), WD is the second brand to offer them. Now we just have to wait for Seagate. (not that I'm interested at all in Seagate, but it'll be good for the competition and hence, the prices)

Maybe you're thinking specifically about Enterprise drives.

Because Seagate were the first to announce and release a 4TB hard drive, almost 1 year ago (end of October 2011). They just don't currently market the drive as retail integrator (bare) product and sell it only in their own enclosure.

Hitachi was the second to announce, back in December 2011 also with encased drives and one model of bare drive, supposedly shipped in January 2012, but I think it might have only hit the street in March 2012. In April 2012 they announced the first Enterprise model.

You're right.
But what I meant was indeed bare drives available for sale.

So.....

I've previously mentioned that space was running low on my current NAS. This past week I got down below 700GB free. Let's call it 650GB. That's been constant for some days now. Until...

Today I get a warning email from the NAS saying space is running low and that I'm currently at 330GB free. Hmmm.. WTF!? Where did over 300GB just disappear to?

I only did one thing yesterday which was out of the ordinary...

Yesterday I re-enabled some Mac-to-NAS rsync backups (from the NAS UI) that I had disabled for some months. I had 2 backup jobs and only one of them would work, so I only kept the one turned on. Since it's RSYNC, it's incremental and most everything already existed on the NAS. The total backup folder was only about 265GB and I can't see more than 20-50GB of that being newer content that didn't previously exist.

I can't see these backups being the missing data. I killed the backup share completely and that gave me some 280GB of additional space. I still think I'm missing 300+ however.

I'm at a total loss for ideas at this point.

There are plenty of disk space graphing programs for Mac. I haven't needed one in a while but when I did, I used "Disk Inventory X." Just use that to drill down to see what's taking up a lot of space.

Disk usage tool for Mac OS X: Grand Perspective (current as of Aug 2012): http://grandperspectiv.sourceforge.net

I'm about to run it now...

I use Disk Inventory X, but also useful is DiskWave, which gives you a multi column hierarchical view of the disk usage that is a bit quicker to navigate when you are looking for large folders rather than large files.

http://diskwave.barthe.ph/

Disk Inventory X looks like it's PPC only as it was last updated in 2005. I can't imagine it would work in Mountain Lion.

I tried a commercial app (in demo mode) just before downloading the other program I pasted the link to. I wasn't able to find any reason for the extra storage use. All the paths I checked on my share seemed like the contained the right amount of data in them.

I'm really perplexed here. If I was able to confirm that the backup path was empty before re-scheduling the backup tasks I could mostly explain away the issue. But it's still not quite the right amount of data and I know for a fact that the path was NOT empty.

I'll keep looking but at this point I can't think of anything definitive other than copying everything off onto other disks and then reformatting the NAS before copying everything back. Not something I'd really want to risk unless it's a verified/checksummed copy onto another redundant array.

http://www.derlien.com/dixforum/viewtopic.php?t=62 - universal Disk Inventory X. (Being open source, you also could just download and compile it for Intel).

Thanks for the tip on DiskWave. I like the treemap view of Disk Inventory X, but it's nice to have something that's under active development and offers a different view.

Oh, Tony, if you haven't bought a Synology yet, this looks like a pretty nice deal.

It's not. While the price is decent, it's one of the "j" models, which means sloooooow. I wouldn't touch it.

Yeah, I guess you're right. The "j" series should be fine for general NAS usage and running Squeezebox server, but if you want to do transcoding, it's probably better to use one of the models with Atom chips.

I was more concerned with the question of whether or not it would accept their expansion bay units. Though the CPU power might be a factor if I decide to ever use any of its server features, such as web server or VPN host. Also, you're right, maybe I'll use it to transcode stuff if I can figure out how to set it up to do that.

Which ones in their inventory have both of those features (compatible with the expansion bay, and also, fast processor)? It's hard to tell from just browsing their web site.

The CPU question is answered here:

http://forum.synology.com/wiki/index.php/What_kind_of_CPU_does_my_NAS_have

Not sure about which ones support the expansion thing

If it's the expansion bay compatible ones you're interested in, you're limiting yourself to only a handful of compatible devices. If you don't use rack mounted devices, and I don't think you do, the only available expansion bays are the DX513 and the DX1211. The DX513 is compatible with 3 NAS units, the DX1211 with two. All the compatible NAS servers are from the "+" series, the most powerful series Synology has to offer (so no problems in the CPU department). Of course, this also means these are the most expensive units.

Eg. (I'll use Euro prices here, but I suspect the situation in dollars will be the same) The DX513 is the cheapest expansion bay and costs about 530 euro. It can be used with the DS712+, the DS1512+ and the DS1812+ NAS units, which cost 410 euro, 700 euro and 840 euro respectively. This means that he cheapest unit, the DS712+, which is only a two-bay unit, combined with the DX513 will cost you 940 euro for 7 bays. This, while a DS1812+ would have only costed you 840 euro, AND would have given you 8 free bays! Not a cost-effective option if you ask me... If you look are the comparison table, you'll notice all those units are from the "Small and medium business range".

In my opinion, the best price/performance offering currently (for home use) is the DS413 unit. It's 4-bay, quite fast and costs about 450 euro. But it cannot be expanded.

To be honest, I find those expansion bays quite expensive by themselves - I think I'd rather invest in a big NAS with a large number of free bays, instead of buying an extra -expensive- expansion bay to go with it. You'll probably be cheaper off in the end anyway. And, if I'm not mistaken, you also cannot combine the disks in the expansion bay and the ones in the main unit into one big volume. You'll need to make (at least) two volumes. This defies the purpose if you ask me.

From what I'm seeing here:

If adding an expansion bay is critical to me, then what I really want is the DS1512+ now, allowing for the option to add the DX513 later.

If later expansion is not important, then I could go with the cheaper DS413 now.

Correct. But you'll be able to buy about two DS413's for the price of one DS1512+.

FWIW, I think 5 bays is a great number that lets you hit the sweet spot for RAID-5 setups (3-4 disks) but still have 1-2 bays open for when you want to migrate to bigger drives and need to copy the data somewhere so you can create the newer, bigger RAID volume.

That's why I was thinking of the Synology system because, if I'm reading it right, I can add drives to the system to increase the overall size without need to copy the data anywhere. So if, for example, I started out with the 5-bay system, I could add the 5-bay expansion and get more space without having to copy everything off it.

Yeah, I guess that makes sense, but I've always felt increasing the size of disks was a better play than adding more disks. Fewer disks == less chance of failures, less power consumption, etc.

Good point there.

This is true. But you could also replace the disks with larger disks one by one and let the array rebuild. Works just as well and is a lot cheaper. Unless you absolutely need 10 disks in your array of course - which would automatically be two volumes, see my earlier comment about that.

Wait, so the expansion bay wouldn't allow me to address all discs as one big storage array?

I thought I'd read that somewhere, but the Synology site suggests otherwise:



So I'm probably wrong. Still, it might not hurt checking before making the final purchase.

I'm also wondering what happens if eg. you're running 10 disks in a 1512+ and DX513 expansion bay and the power drops by accident on the DX513. In that case, more than one disk is "lost", which is more than RAID5 can handle.
Would that mean the entire array would be lost and all the data gone? In that case I would surely also invest in a big fat UPS, just to make sure!

Good question about the power loss. I'm going to post that question to their forum (if I can't find it through searching).

The array will probably go offline until power is restored to the expansion. Should be the same as pulling multiple drives from a single box. It won't destroy the array. But don't quote me on that, I've never used Synology-specific RAID/NAS before.

I hope you have plenty of patience, traffic can be pretty slow there.

FWIW, regarding transcoding, I am having no problems using the built in Audio Station app (on a DS710+) to transcode FLAC to MP3 to stream to my XBox while the NAS is performing its normal duties (serving 3 other computers plus rsync backups).