ZFS on Hardware RAID

[andy thomas]

On Sun, 20 Jan 2019, Ireneusz Pluta wrote:

> W dniu 2019-01-20 o?09:45, andy thomas pisze:
>> I run a number of very busy webservers (Dell PowerEdge 2950 with LSI 
>> MegaRAID SAS 1078 controllers) with the first two disks in RAID 1 as the 
>> FreeBSD system disk and the remaining 4 disks configured as RAID 0 virtual 
>> disks making up a ZFS RAIDz1 pool with 3 disks plus one hot spare. 
> In this configuration, have you ever made a test of causing a drive failure, 
> to see the hot spare activated?

Yesterday I set up a spare Dell 2950 with Perc 5/i Integrated HBA and six 
73 GB SAS disks, with the first two disks configured as a RAID 1 system 
disk (/dev/mfid0) and the remaining 4 disks as RAID 0 (mfid1- mfid4). 
After adding a freebsd-zfs GPT partition to each of these 4 disks I then 
created a RAIDz1 pool using mfid1p1, mfid2p1 and mfid3p1 with mfid4p1 as a 
spare, followed by creating a simple ZFS filesystem.

After copying a few hundred MB of files to the ZFS filesystem, I yanked 
/dev/mfid3 out to simulate a disk failure. I was then able to manually 
detach the failed disk and replace it with the spare. Later, after pushing 
/dev/mfid3 back in followed by a reboot and scrubbing the pool, mfid4 
automatically replaced the former mfid3 that was pulled out and mfid3 
became the new spare.

So a spare disk replacing a failed disk seems to be semi-automatic in 
FreeBSD (this was version 10.3) although I have seen fully automatic 
replacement on a Solaris parc platform.

Andy