Expanding ZPool - Just Checking

[feleven]

I'm about to expand my zpool by moving from 4 x 1TB WD-Reds in RAIDZ2 to 6 x 2TB WD-Reds in RAIDZ2. From all I've read, and what I *think* I understood, I can (after ensuring my backup is solid, safe and current, and my zpool "autoexpand" parameter is set "on"):

1) replace 1 drive at a time for the existing 4, then add the 2 new drives as VDEV2 - with the understanding that if either drive in VDEV2 fails, my zpool is toast (not my first preference)

2) just shut down the machine, replace the 4 x 1TB drives with 6 x 2TB drives, configure the 6 drives as 1 VDEV in RAIDZ2, then restore the backup to the new drive system

Preferring to measure twice and cut once, I thought I'd ask for a check of my thinking: did I misunderstand anything? Is there a better way to do this that I should consider?

[ Yes, I know - both $/GB and future-expansion-hassle-factor fall if I get bigger drives - budget constraints have been applied. ]

My MoBo has 6 native eSateIII ports, and I've installed a PCIe card with 2 more eSateIII ports, for a total of eight. I have a second cooling fan ready on the shelf if airflow with the existing fan isn't enough. My PSU should be "sufficient" at 750W.

I'm planning to use 2 of the liberated 1TB drives as a single backup volume, recognizing that I'll have less total backup space than total primary drive space. My current backup consumption is only 200GB, and will double in the near future - the drive is a single 500GB non-NAS Seagate. I'm not as confident in my understanding for this setup: is a simple mirror the optimum backup drive configuration? Or should I just go JBODs for the larger capacity?

I was gonna just do the drive upgrade on my own, as my data is backed up in several places so even a total screwup on my part wouldn't be the end of the world. But it occurred to me that THIS is the time to nail down my understanding of my drive configurations, and do the upgrade right the first time.

Any input welcome. Thanks!
Rod​

[ My apologies - I had posted this previously in a non-titled area of Help & Support by mistake. I've moved it here as its more an Installation issue than anything else. - R ]​

 

[DrKK]

I'm about to expand my zpool by moving from 4 x 1TB WD-Reds in RAIDZ2 to 6 x 2TB WD-Reds in RAIDZ2. From all I've read, and what I *think* I understood, I can (after ensuring my backup is solid, safe and current, and my zpool "autoexpand" parameter is set "on"):​

​

1) replace 1 drive at a time for the existing 4, then add the 2 new drives as VDEV2 - with the understanding that if either drive in VDEV2 fails, my zpool is toast (not my first preference)​

​

2) just shut down the machine, replace the 4 x 1TB drives with 6 x 2TB drives, configure the 6 drives as 1 VDEV in RAIDZ2, then restore the backup to the new drive system​

​

Preferring to measure twice and cut once, I thought I'd ask for a check of my thinking: did I misunderstand anything? Is there a better way to do this that I should consider?​

​

[ Yes, I know - both $/GB and future-expansion-hassle-factor fall if I get bigger drives - budget constraints have been applied. ]​

​

My MoBo has 6 native eSateIII ports, and I've installed a PCIe card with 2 more eSateIII ports, for a total of eight. I have a second cooling fan ready on the shelf if airflow with the existing fan isn't enough. My PSU should be "sufficient" at 750W.​

​

I'm planning to use 2 of the liberated 1TB drives as a single backup volume, recognizing that I'll have less total backup space than total primary drive space. My current backup consumption is only 200GB, and will double in the near future - the drive is a single 500GB non-NAS Seagate. I'm not as confident in my understanding for this setup: is a simple mirror the optimum backup drive configuration? Or should I just go JBODs for the larger capacity?​

​

I was gonna just do the drive upgrade on my own, as my data is backed up in several places so even a total screwup on my part wouldn't be the end of the world. But it occurred to me that THIS is the time to nail down my understanding of my drive configurations, and do the upgrade right the first time.​

​

Any input welcome. Thanks!​

Rod​

[ My apologies - I had posted this previously in a non-titled area of Help & Support by mistake. I've moved it here as its more an Installation issue than anything else. - R ]​

OK.

I'm going to try and answer this. It's a lot to read. I'm going to repeat back what I think you're saying, and give you a yes or no.

You say: You want to replace in your existing 4 drive pool, each drive, one at a time, with a drive of larger capacity.
I say: Yes, that will work. Replace them one at a time, give them a chance to resilver between each replacement.

You say: You're going to make a second vdev, and that vdev is going to be a **STRIPED** vdev of 2x2TB drives, and then you're going to have a 2-dev zpool. This is VERY VERY VERY VERY VERY VERY strongly discouraged. As you are aware, you will lose ***ALL THE DATA ON THE WHOLE ZPOOL*** should you drop EITHER of these disks.
I say: You will be in ****MUCH**** better shape of you take that second pair of drives, and MIRROR them, as a mirrored 2nd vdev. This will cost you 2TB of space, of course, but Jesus Christ, your risk will decrease by 99%, to the WHOLE POOL.

The rest of it---whatever, sounds fine.

 

[DrKK]

So yeah rereading this, just one more point, the only thing that will be RAID-Z2 is the first vdev.

That second vdev will be on its own, either striped to 4TB, or mirrored as 2TB. Not part of the RAID-Z2. Hope that's clear.

 

[feleven]

Thanks DrKK, although I guess I wasn't clear.

From my reading, I understood having two VDEVs is not encouraged, and sort of last resort if there's no other way - this is why I added the parenthetical "not my first preference". What I was asking was whether I understood this correctly. Judging from your answer, I did understand this correctly.

Overall, I was trying to say I thought I understood I had two choices 1) OR 2), with 1) not being the best.

1) meant I could avoid having to restore the backup because I just replace each of the 4 1TB drives with a 2TB drive, one at a time - but I end up with two VDEVs which is dangerous to my data. Again, not my preference.

2) meant I could just forget about the data on the existing 4 x 1TB drives, remove them, and do a wholesale replacement of them with the 6 new drives in a single VDEV 6-drive zpool, THEN restore my data to the new 6-drive zpool from the backup.

Again, judging by your answer, it seems I understood both options and the benefits and dangers of the choice. So I got my answer. Much appreciated.

My 2nd question was about the backup drive configuration: 2x1TB mirrored? or 2x1TB JOBD? The backup drives are physically separate from the main data storage, so I was looking for advice on the best way to set them up, if there IS a best way. That's all.

 

[warri]

You are right about your two choices, and choice 1 wouldn't be a good idea as DrKK already explained.
The alternative sounds a lot better.

A backup on JBODs is better than no backup, but since disks often decide to fail in the wrong situation I'd always prefer a redundant pool (e.g. mirror) for backups.

 

[feleven]

Thanks for the confirmation, warri. The learning curve on FreeNAS has been steep, even with a long-ago-experience with a unix system. The manual and cyberjock's tutorials help a lot, but it never hurts to double check one's thinking when it comes to foundational elements like drive configuration when doing first installation or a significant upgrade. I went ahead and did option 2 from my choices, and will do the backup replacement later today. This forum gives us semi-noob's a fighting chance to do things right, as well as learn something, before making serious mistakes. Your input was most appreciated.

Rod