Upgrade my RAIDZ array by replacing disks or backup & restore?

Craig321

Craig321

Craig321

Soldato
Joined
2 May 2004
Posts
19,950
Hi,

I'm looking to replace my 2 old 1.5TB drives (recently found out they're 6 years old and I simply don't trust them :eek:). Currently they are in a RAIDZ1 array with two other 2TB disks which are a couple of years old each.

Do I:
Replace one with a new disk, wait for the array to rebuild, then do the other. This means 2 rebuilds of a 3.9TiB array which is 75% full.

Or:
Back everything up to my 4TB external and build a brand new array on the 4 2TB disks? This means 0 rebuilds, but 3.9TiB of writes back to the array once created.

I'm thinking option 2 as it's going to put less stress on my existing 2TB drives... I wouldn't really want to put them through 2 rebuilds in the space of a few hours, or would it be OK?

Thanks
 
I'd just go option. ZFS rebuilds are far less stressful than regular raid rebuilds.

ZFS is aware of where and what data is on the drives so it only rebuilds the where there was data stored. Other RAID options have to rebuild block by block.

I guess it depends what sort of data you are storing. Anything critical then use the external, but for me mine is a media so not a great deal if I we're to lose it all
 
Last edited:
Data loss isn't an issue as either way I'd have it backed up to the external (plus I have CrashPlan for unrecoverable stuff), I'd just like to go for the least stressful method for the existing 2TB drives.

I didn't realise ZFS only rebuilt where there's data. That means it may actually be less stressful to rebuild twice than copy all 3.9TiB back over?
 
Craig321 said:
Data loss isn't an issue as either way I'd have it backed up to the external (plus I have CrashPlan for unrecoverable stuff), I'd just like to go for the least stressful method for the existing 2TB drives.

I didn't realise ZFS only rebuilt where there's data. That means it may actually be less stressful to rebuild twice than copy all 3.9TiB back over?
Click to expand...

If my fag packet maths is correct yes

IIRC it will also balance the reads across the remaining drives it's rebuilding from so it will read 1.3TB from the existing drives and write what it needs to on to the fresh drive.

Where as backing up to an external would mean a read of a similar amount followed by the additional writes to each drive
 
I've done this before and in fact I'm doing it again very soon. Last time I replaced 3x1tb with 3x2tb and expanded into the extra space.

It's reasonably quick and if you want to be extra safe you could do a scrub after each resilver
 
How did your rebuild go? After starting the rebuild of my first disk I had a disk go offline (dodgy sata cable). Then on the second disk I got an Uncorrectable Read Error.

Luckily it was RAIDZ2 so it didn't cause a problem although I think I need to run regular SMART tests :eek:

I'm now sold on the idea that RAID5/RAIDZ1 is not much use any more with the high capacity consumer drives.
 
Uhtred said:
How did your rebuild go? After starting the rebuild of my first disk I had a disk go offline (dodgy sata cable). Then on the second disk I got an Uncorrectable Read Error.

Luckily it was RAIDZ2 so it didn't cause a problem although I think I need to run regular SMART tests :eek:

I'm now sold on the idea that RAID5/RAIDZ1 is not much use any more with the high capacity consumer drives.
Click to expand...

How often do you scrub your pool? Depending how often you need do it will also point out any errors
 
You must log in or register to reply here.
Back
Top Bottom