XigmaNAS

Ok, here's the deal.

3x1.5 Tb disks in a raidZ1 config. I wish to grow it. I know that one could replace drives one by one and re-silver every time a disk gets replaced.

My idea is to buy one disk at a time - I know this would only grow the pool once I get the last 1.5 Tb drive replaced... however, I am thinking of buying drives say every 6 month. Here's the pattern:

1.5 1.5 1.5 = useable space ~3 Tb
1.5 1.5 2.0 = useable space ~3 Tb
1.5 3.0 2.0 = useable space ~3 Tb
4.0 3.0 2.0 = useable space ~4 Tb

and this way gradually grow every time replacing the smallest disk with the best value... mind you at the time I think the 3Tb Red NAS is the best value for money. But I do not plan to buy 3 of them all at once.

Any pros and cons regarding the above?

Makes sense? Or stupid thing?

Thanks
D.

I believe I read that the 3TB WD Reds had some reliability issues, that were NOT present in the 1, 2 and 4 TB models. I would go for 4TB drives as replacements if I were you (IMHO!) - especially as the price will fall over the 18 months you plan to buy them.

In my own case, I bought 4 x used 1TB WD Red drives at about £30 GBP each, to replace a mixed selection of 4 x 0.5TB drives - worked a treat! and cheap too! SMART reports no errors at all.

(BTW: I use an HP N40L - the arch-rival to the Dell T20 !! - although I see in another thread about slow transfers, you have a Xeon CPU - very envious !!! )

mooblie wrote: (BTW: I use an HP N40L - the arch-rival to the Dell T20 !! - although I see in another thread about slow transfers, you have a Xeon CPU - very envious !!! )

I have az HP Micorserver N40L - this is what I replaced it with. I plan to use that for something else But it ran reliably for 5 years now I had version 9.3.0.x on it and did not want to mess around any longer. The T20 I bought exactly due to the CPU. I was looking at the new microserver, but due to Xeon I chose the T20.

Hm, will read on, never seen the Red NAS series to have any issues. I need to start getting new drives soon, my old ones I don't even dare to say how old they are or what brand...

I think the survey I was thinking of is here:

https://www.backblaze.com/blog/hard-dri ... r-q2-2015/

Maybe it was Seagate 3TB to avoid!

Actually I read that the 3Tb WDs have 2 platters, but only 3 heads. The 4th head is replaced with a little balance piece. This makes it assymmetrical and actually quite bad for any non-symmetric setups.

On the other hand, I was wondering, If I would go and replace these 1.5 Tb drives one by one with 3 Tb disks, I'd lose the 4k option straight away, correct? That would only work if I were to format the 3 new drives and create a new pool...

I don't know about that. Hopefully someone else here will jump in...

Danzi,

Like you, I've read for YEARS that ZFS will automatically expand when adding larger drives. As you were saying...

4.0 3.0 2.0 = useable space ~4 Tb

when that third drive gets replaced with a larger drive, the pool will become larger.

However, the other day, I was playing with a test server, trying this very concept. When I offline-ed the smallest drive, and replaced it with a larger one, then did a I was surprised to see the pool size didn't automatically expand.

I googled the issue and discovered something I hadn't seen before. The set autoexpand command. So, I did a:
...fully expecting the pool size to recalculate. It didn't. More googling. I then read I needed to:
TaDa! The pool size increased. I then replaced the next smaller drive with a larger drive, using the offline/online -e commands, and the pool size automatically expanded.

Now, I'm not sure if just the -e parameter is needed, or if one needs both the autoexpand AND the -e parameter, for the pool size to increase. I'll leave that as an exercise for the student.

Gary

autoexpand ON BEFORE replacing the first disk, the pool size automatically expanded.

If autoexpand is OFF BEFORE replacing the first disk, online-e is necessary for the pool size to increase.

sleid,

Thanks for the clarification. That makes perfect sense.

Backblaze's drive data page is here: https://www.backblaze.com/b2/hard-drive-test-data.html

This has links to all their drive reliability articles and most recent data. I bought 6 Seagate 4 TB drives based on their statistics.