Replace existing drives vs. Replace System

[SoonerLater]

I have a FreeNAS box that I built in April 2013 using an HP Proliant N40L computer that has 4 drive bays with quick-release caddies (but not hot-swappable) and two more drive bays that can be used to fill with a total of six drives. I installed 16 GB of DDR3 ECC Ram and six WD Green 7200rpm 1 TB drives (wdezrx). The system is setup as a Z2 Pool. I can lose two drives before I lose data. The CPU is a AMD Turion(tm) II Neo N40L Dual-Core Processor. It's the Little NASengine That Could. And it has always served me well. I've never had a complaint about its performance. I don't run any jails. I don't run Plex or anything else on this. This just acts as a file server (mostly for media files). At most there are four files being served up to different users, but most of the time there's just one file operation going on. I don't mind spending the extra for the Pro drives if there's a reason to do so, but I wonder if I didn't make a mistake last time buying 7200 rpm drives. I bought Green drives last time because I was concerned about the ability of the power supply to run everything. That might still be an issue that I need to figure out.

Seeing as how this is about to have its 8th birthday and storage is over 80%, I should either replace all the drives or replace the entire system. If I just replace the drives, I would either buy 6 qty. WD Red Plus (5400 rpm - $119 each) or WD Red Pro 4 TB (7200 rpm - $139 each) drives. So before tax, it's either $714 or $834. Is there a good reason to buy the Pro (7200 rpm) drives?

Then there is the system. I'm inclined to not do that at this point. If the system dies, I can live with several days of downtime while I go buy a new 6 bay (or larger) enclosure system. And then I'd just install TrueNAS on the new system (on an SSD; whereas now the OS is on a USB drive) and then put all the new (2021) drives in it and let it go. I've had to replace the boot USB drive before. None of my pool is encrypted. It should (in theory) be easy to move the new (2021) drives to a new system and then just keep on trucking.

Any suggestions before I order six new drives?

Oh, and my plan is (1) shut down system, (2) replace one drive, (3) reboot system, (4) when Truenas notices that a drive from the RAID is missing, I'll add the new drive to the RAID and let it flood the data to it ("resilver?"). When that's done, I'll repeat that process five more times. Perhaps one drive a day. When it's running all six new drives, then I'll resize the array to take advantage of the larger drives. Then I should have around 16 TB of effective storage, which will satisfy my needs for many years to come.

Oh, and this box runs FreeNAS-9.10.2-U6 (my other runs FreeNAS-11.2-U8, but it's still a baby).

 

[SoonerLater]

I suppose that I could buy just five 4 TB drives and run them as a Z2 pool which would give me 12 TB capacity, which is triple what I have now. Five running drives would require less power than six, so that helps.

What I don't know is whether I can go from a six drive Z2 pool to a five drive Z2 pool without having to backup everything in the old pool, then create a brand new empty pool, then restore the data to the new pool. Is it possible under any version of TrueNAS (much less 9.10.2-U6) to do this on the fly (replacing one drive at a time, but stopping after the 5th drive)?

 

[Etorix]

No, the pool geometry cannot be changed. If you replace five 1 GB disks by five 4 GB disk and remove the sixth disk you will end up with a degraded RAIDZ2 of 4 GB drives capped at 1 GB by the ghost of the last 1 GB drive.

 

[SoonerLater]

No, the pool geometry cannot be changed. If you replace five 1 GB disks by five 4 GB disk and remove the sixth disk you will end up with a degraded RAIDZ2 of 4 GB drives capped at 1 GB by the ghost of the last 1 GB drive.

Thank you for clearing that up. I'll buy six drives... as soon as I can verify that the electrical current draw of six Red Pros (or Red Pluses) won't be greater than my existing power supply can handle. It's been eight years, but I think that I bought WD Green drives before out of concern for the current draw on the power supply.

ADDED: The WD Green 1 TB drew 7.4 watts at read/write, but the WD Red Pro 4 TB draws 7.2 watts, so this should work fine.

 

[Etorix]

There's no compelling reason to go for Red Pro over Red Plus. Just be aware that the Red Plus actually spin at 7200 rpm but are labelled "5400-class" by WD marketing. Get the cheapest drives you find as long as they are not SMR!

If you have spare SATA ports, the best way to replace the drives is to plus new ones without removing the old ones and select "replace" in the GUI. That way there is no loss of redundancy during resilvering and it's possible to replace several drives at the same time (number of ports permitting). Then take out the old drives and repeat as many times as necessary.

 

[ChrisRJ]

ADDED: The WD Green 1 TB drew 7.4 watts at read/write, but the WD Red Pro 4 TB draws 7.2 watts, so this should work fine.

Those figures are only partly relevant, since they are the power consumption during regular operation. The critical value for sizing of the power supply is what they draw when the system is turned on. That current will be considerably higher. @jgreco has written a nice guide on this subject: https://www.truenas.com/community/resources/proper-power-supply-sizing-guidance.39/