Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

I want to understand and if it makes sense, disable the alert message I receive about spares missing on my ubuntu linux software raid 5.

I used mdadm and set up a /dev/md0 raid volume made up of 3 hard drives.

I then set up email alerts so I can see when there is a problem with it.

I often get these 'spare missing' alerts, and I assume that means there is a second spare defined and I do not have one.

I am looking to clarify that this is actually not really a problem, and that I can change a setting to tell mdadm I do not have a second spare (I have only 3 drives). My system should continue running if 1 drive goes down?

Here is the alert message:

This is an automatically generated mail message from mdadm running on myserver

A SparesMissing event had been detected on md device /dev/md0.

Faithfully yours, etc.

P.S. The /proc/mdstat file currently contains the following:

Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid5 sdc1[1] sdb1[0] sdd1[2]
      1953519488 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices: <none>
share|improve this question
    
How is the group defined in mdadm.conf? –  Shane Madden Sep 6 '11 at 16:13
    
DEVICE partitions ARRAY /dev/md0 level=raid5 num-devices=3 spares=1 UUID=80c8bec2:d8660d29:ae8962f 2:b7b9c495 , so I assume spares=0 would fix it, but is there a negative to this? A spare is optional, correct? Raid 5 means if 1 drive goes down the other 2 will keep running, correct? –  Scott Szretter Sep 6 '11 at 17:04
    
So is it safe to set it to spares=0 ? –  Scott Szretter Sep 9 '11 at 12:03

1 Answer 1

up vote 0 down vote accepted

Yes, set to 0 spares; a RAID 5 group will be able to tolerate 1 failure of an active disk. A spare is used as a reserved disk to immediately start rebuilding the array if one of the active disks dies.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.