Do I need to rethink this/help me rethink this/is this possible?

[mcleanrs]

My current setup is very very similar to the one outlined HERE, except that I'm using a different SATA controller and I'm using larger drives.

and for those who don't clickthrough...

• HP Minitower (2 3.5" bay, 3 5.25" bay)
• Pentium 4 2.8 Ghz
• 4 gig Crucial RAM
• Promise SATA300 TX4 4-port SATA controller
• 2xSamsung Spinpoint 2tb 7200 RPM
• HP 4g USB thumbdrive

Ok...here's the glitch. Even though I'd read a bit about FreeNAS and ZFS, somewhere in my mind I thought I could add drives and expand the array later on. I was wrong.

Right now I am using 2x2Tb drives for a net of 2Tb usable space.

As I understand, my only real upgrade path in the future would be to add 2 more drives, but because of the way ZFS works...adding 2 more drives would only give me 4Tb of usable space, right? And while I would be able to have 2 drives fail in this scenario without data loss, this would be ONLY if the right two drives failed -- mainly one from each "set"

Soooo...what should I do? Here are some scenarios I've thought of. Feel free to add your own.

1 - Do nothing right now. Worry about it when I have filled my first 2 tb, and hope that the ability to expand a set has come to FreeNas by then.

2 - Bite the bullet and step up to 5 drives right now. Right now I have an extra 2 Tb hard drive that I could use, to migrate the data onto temporarily. This would involve adding another Promise SATA300 Tx4 card as well. In the end I'd have some extra SATA ports left over, but I figure this way I'd also have 2 cards on hand in case one failed. There are also SATA ports on the computer's motherboard, just 2 I think.

3 - Fill the first 2 Tb. Then buy 4 additional drives (For a total of 6) and upgrade to a 5 drive set. Use one of the 2 Tb drives to hold the data temporarily while I destroy and recreate the set, and then set that drive aside as a spare to have on hand.*

*(I realize that I could potentially lose data if there was a problem with the single drive holding all my data during the migration. The first 2 Tb will be mostly a backup of my day-to-day system. So if I happened to lose my backup in the shuffle...it's just a backup anyway, I'll just re-backup)

 

[matthewowen01]

that's a lot to process. to recap, you have a system it's static and you're wondering about how to design your storage pools.

Currently you have 2, 2TB drives mirrored. if you were to add 2 more drives (same size, not necessarily 2 TB though) to your pool in a mirror. with this, you could only safely loose 1 disk. it is possible to loose 2 if they are both from the separate mirrors.

I'd make your upgrade now and all at once, rather than waiting. Scrub your mirror, just in case make sure everything is good. buy your 4 new 2 TB drives. i am going to make an assumption that your current mirror is not filled. Use dd to create a Large file on your mirror, dd if=/dev/zero of=tempDisk bs=2048 count=50M, that will create a 100GB file which we will use as hard disk, you can make it bigger if you need too. Now break your mirror you should have 5, 2TB disks that are unused, a degraded mirror with a 100GB file on it. now comes the fun part. create a new raidz2 pool from the 5 and the tempDisk, zpool create -o autoexpand=on myNewPoolName raidz2 disk1 disk2 disk3 disk4 disk5 /yourOldMirror/tempDisk, you'll have a new pool created but it's size will only be 400 GB. now copy your data from your broken mirror to the new pool. once it's safely moved over, replace the tempDisk, zpool replace myNewPoolName tempDisk disk6, your pool will start to resilver and once it is done, you can check the status with , zpool status, export the pool then import it, all your 8 TB will be available.


if you are unclear or need any help please let me know.

 

[mcleanrs]

Well let me tell you what's on there right now:
1 - Some media that's also housed on a USB hard drive and...
2 - About a week's worth of TimeMachine backups for my MacBook Pro.

Altogether it's about 600 gig worth of stuff.

So here's what I'm thinking instead, mostly because I don't feel intimidated by it.

But first let's say that I already have drives "1" and "2" in there, and the new drives are going to be "C" "D" "E" "F"

Buy 4 more drives (C,D,E,F).
Now remember that the case only has room for 5 drives, but I'll have enough SATA ports that I could potentially hook up more than 5, temporarily.

So attach drive "C" and copy everything from the 1/2 set to "C"

Then add D, E, and F, and erase 1/2. Create a new set that's {1,2,D,E,F} (You like how I keep changing my syntax here. This is why I'm not a coder, I just play one on TV).

Then copy everything from "C" onto the new set {1,2,D,E,F}. Remove "C" and set it aside as a spare.

Is that reasonable?

Also, any advantage to buying another SATA controller...or would using 1 of the onboard ports with the other 4 on the Promise card be ok. Or in other words, will I have a performance penalty by using one of the onboard ports?

 

[matthewowen01]

first up, you can cram 5 drives into 3, 5 1/4, bays.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817332011
here are some smaller ones that are a bit cheaper:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817332010
http://www.newegg.com/Product/Product.aspx?Item=N82E16817332009

i have the 5 in 3 and loved it until i switched to a server 4U server case with 20 hot swap sata bays in the front.
http://www.newegg.com/Product/Product.aspx?Item=N82E16811219033

however if you want to stick with 5 drives, your plan sounds good. i would recommend a raidz2 for 2 drives of redundancy.

as for the controller card, the onboard should work great, the PCI card you have will be a bottle neck if you are going for speed. swap it out for a pci-e card if you can.
http://www.newegg.com/Product/Product.aspx?Item=N82E16816124027

 

[mcleanrs]

So I think the mini-tower is PCI only, and won't do PCI-E. That's what I get for building this on an ancient machine! But fortunately so far my network is the bottleneck, so this machine will work for now.

The 5 in 3 looks interesting! That would let me put 7 drives total in the machine, but I thought that I saw somewhere that 5 is good and 6 is good but 7 is less than ideal. Maybe I can go dig up where I saw that and you can tell me if it's just a big lie. I guess I could do 6 drives with 2 redundant plus a hot-spare? I'm the "by default" administrator over some 8-drive Raid5 linux boxes at work (That were purchased before my time and are running a strange proprietary build of Red Hat), so long story short...it would be safe to say that I know just enough about this stuff to be dangerous.

 

[Tekkie]

The 5 in 3 looks interesting! That would let me put 7 drives total in the machine, but I thought that I saw somewhere that 5 is good and 6 is good but 7 is less than ideal.

Do you mean this thread: http://forums.freenas.org/showthread.php?16-Getting-the-most-out-of-ZFS-pools!

 

[mcleanrs]

That would be the one. I revisited it and I'm still confused, though after a second reading I'm thinking maybe 6 is the magic number?