rook01

Question about RAID 5 and power

Recommended Posts

Hello, I am trying to create a RAID 5 music server that will hold all of my music and will then be streamed over ethernet throughout the house.

I have read somewhere that a power failure has the potential to 'mess up' the parity on the RAID 5 array and therefore lose the data. I haven't been able to find any more information on this, so I figured I would ask here because this group seems to be pretty knowledgeable.

So my questions are:

1. Is it true that a power failure can corrupt the parity on the drives?

2. Does the above hold true only when writing to this RAID 5 array, or can the same thing happen during reads?

Thanks in advance,

Derek

Share this post


Link to post
Share on other sites

I'm actually not worried, mainly becasue of a UPS as Joe mentioned.

I'm just wandering if what I heard was true.

I'm also going to ask another question with the disclaimer that I am still learning about raid...

Suppose I had to move the RAID 5 array to a new location and had to un-plug it for a long period of time. Assuming that I shut down windows and the computer before unplugging it, would leaving the RAID 5 array without power for a long time have any effect on the data on the hard drives?

Thanks in advance,

Derek

Share this post


Link to post
Share on other sites

An unexpected power failure on any computer system can cause data loss or system corruption. Just make sure you are using a good UPS.

I have never heard of losing the Raid array by shutting it down (properly ofcourse) and moving it to a different location. I have done this with no problem.

Another feature you might look into is Battery Backup Module for the raid controller if it supports it.

Share this post


Link to post
Share on other sites

I move hardware raid arrays from server to server all the time without any issues at all, and software raid arrays from server to server when I have no other choice, as they don't transplant quite as well.

Michael

Share this post


Link to post
Share on other sites

Well, I guess since none of our experts have spoken up, I'll give it a shot...

1. Is it true that a power failure can corrupt the parity on the drives?

199419[/snapback]

I can see how this would be true. A write on a RAID5 set involves reading the parity block, recalculating parity, and then writing the data + parity blocks. If power fails after one write has completed but not both, then you've got corruption.

2. Does the above hold true only when writing to this RAID 5 array, or can the same thing happen during reads?

199419[/snapback]

If no writing is taking place I don't see how corruption can happen...

Suppose I had to move the RAID 5 array to a new location and had to un-plug it for a long period of time. Assuming that I shut down windows and the computer before unplugging it, would leaving the RAID 5 array without power for a long time have any effect on the data on the hard drives?

199419[/snapback]

Again, I don't see how.

However, I have heard a few stories where drives that run 24/7 in servers fail when shut down and/or moved. I have not experienced this myself, though.

-JoeTD

Share this post


Link to post
Share on other sites
Well, I guess since none of our experts have spoken up, I'll give it a shot...

I don't know what make YOU the expert...if you just confirmed what I said above.

Share this post


Link to post
Share on other sites
Well, I guess since none of our experts have spoken up, I'll give it a shot...

I don't know what make YOU the expert...if you just confirmed what I said above.

199551[/snapback]

First of all, it was a joke. Second, I didn't say I was an expert. In fact, my statement was supposed to imply that I wasn't an expert. Third, "expert" may have been a poor choice of word, I was simply noting that none of the big names(such as blakewry, Gilbo, etc) had made any comments.

Fourth, if by "confirm" you mean explained why, then yes. You may have answered his question, but your statement was quite broad. I was trying to explain when it was and wasn't true.

Anyways, if you were insulted by my statement, then I certainly do apologize.

-JoeTD

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now