Help restoring 3 disk Raidz1 (or not...) or change to mirroring - how?

[Tim1962]

Hi as in this thread...

https://forums.freenas.org/index.ph...505130355-new-smart-alerts.32738/#post-203874

One of my 3 disk Raidz1 disks has got Smart alerts, and although not necessarily true (see the thread) I feel happier starting again, and have taken delivery of 3* 3Tb HP Red drives...

My current system is an HP Microserver with 3 disk *2Tb Raidz1 with a logs drive 250Gb FreeNAS9.3 8Gb Ram

Looking at other threads Raidz1 seems to be frowned on these days, in favour of mirroring...? Correct?

So I have one failing 2Tb drive, and three new 3Tb drive.

I have read how to replace the current 2Tb with the 3Tb etc, but can / should I convert to mirroring instead at this point. (I could buy a 4th 3Tb drive if warranted). (I don't really expect to need more than 4-5Tb in forseeable future)

Final thing, to make life easier can I remove the log drive to physically make room whilst swapping the other drives

So
1. Replace current Raidz1? (I'll follow documented instructions.)
2. Convert to Mirroring (How?)
3. Temporarily remove Logs Disk (is it OK?)

Cheers
Tim

 

[jgreco]

RAIDZ2 or RAIDZ3 with a larger number of drives is able to give you more space at lower performance. Mirrors give you less space and higher performance.

 

[Robert Trevellyan]

Looking at other threads Raidz1 seems to be frowned on these days, in favour of mirroring...? Correct?

Not exactly. RAIDZ1 is generally frowned on for drives larger than 1TB, although at least one prominent member of the forum (@DrKK ) wouldn't hesitate to use RAIDZ1 for a modest system like yours.

However, since you now have a total of 6 drives, only 1 of which has shown signs of failure, you have a perfect opportunity to build a RAIDZ2 pool of 4 or 5 drives, depending on how many bays your case has. ZFS will behave as though all your drives are the size of the smallest, but you could replace the 2TB drives one at a time for 3TB drives whenever you feel like it (or whenever one fails).

As @jgreco pointed out, mirrors offer better performance, but in a 4-drive system RAIDZ2 is more reliable than two 2-way mirrors. The reason is that with mirrors, you can only afford to lose one drive from each mirror, but with RAIDZ2 you can afford to lose any 2 drives.

Why do you have a dedicated SLOG device?