Question Dead drive in NAS with RAID 5 - Couple of questions...

liberty610

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Hi all,

I have a Western Digital PR4100 NAS unit with 4 of the WD Red 8TB disks in it. The NAS is configured in RAID 5. I just lost a disk in it yesterday, and it is under warranty so I RAM'ed it, but also ordered a brand new one that should be here tomorrow.

Everything that is on this NAS system that is of any importance to me is already backed up to other offline drives so if I loose the entire eray before the new disk gets here, it's not going to ruin my day.

I think this NAS supports hot swap, so I should be able to just remove the dead drive and put in the new one, but I have a couple of questions about that.

1.) Should I leave the NAS system up and online like normal? Or should I shut it down and wait for the new drive to come in?
2.) If I should leave it online, should I shut it down and remove the dead drive, and then reboot it? Or should I leave the dead drive in until I can hot swap it out for the new one?
3.) If I should/can leave it online, should I try and limit my use on it until I get the new drive? I do have a few things on it that are not backed up to other drives, but they are nothing crucial to me. However, I was thinking about backing them up anyways just in case. but the NAS is obviously responding/performing slower then it should be.

Thanks in advance for any replies!
 

USAFRet

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Hotswap is always more hazardous than swapping drives with power off. Even if your hardware supports it.
And I absolutely would not do it on your first attempt, with some data that does not already exist elsewhere.

Power OFF
Swap the drive
Power UP

The RAID 5 array should rebuild itself.
I absolutely wouldn't use it while it is rebuilding.

How much data is in this array?
From my previous experience doing this on my QNAP, rebuild time is about 1-1.5 hours per TB.
 
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liberty610

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There is quite a bit on it. It's a 32TB total (4 drives of 8TB) and there is roughly only 11TB free.

So, for installing the new drive, I will be sure to power it down and put the new drive in and let it rebuild. What about the current time? Should I power it off and take the bad drive out and reboot? Power it off and leave it off?
 

USAFRet

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There is quite a bit on it. It's a 32TB total (4 drives of 8TB) and there is roughly only 11TB free.

So, for installing the new drive, I will be sure to power it down and put the new drive in and let it rebuild. What about the current time? Should I power it off and take the bad drive out and reboot? Power it off and leave it off?
Power off
swap drives
power up and boot up, and the RAID array should start to rebuild itself.

If it does NOT, you may have to invoke that rebuild manually.
My QNAP started the rebuild automatically. Your NAS OS may be different.


You can leave the dead drive in there for now, until you get the replacement.
 
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liberty610

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So, I got my new drive today, and it was D.O.A.

Looking further into a new drive to order, I noticed that there was some issues with WD Red drives where they changed a bit since the last time I ordered drives for my NAS.

I am seeing that there are Red PLUS drives on top of the standard and pro drives. This is where I am not sure what to do. I bought my 4 drives that had 8TB each on them a couple years ago. Can I buy a Red PLUS drive for my replacement if my other 3 drives are Red Standard?
 

liberty610

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4x 8TB drives in RAID 5 would give capacity ~ 22TB (7.27TB per drive, 3 drives for data, 1 drive for parity).

If you have more than 22TB, then it's not RAID 5. It's either RAID 0, JBOD or Spanning.
I am aware of this. I was saying the total of all 4 drives was 32TB. I know that in RAID 5 east away at some of that space.
 

liberty610

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WD is telling me not to do it if the RPM and Cache sizes of the drives are different. All the Red Plus drives I am seeing online are 7200RPM and my drives are all the Red Standards with 5400RPM and 256 cache.
 

USAFRet

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WD is telling me not to do it if the RPM and Cache sizes of the drives are different. All the Red Plus drives I am seeing online are 7200RPM and my drives are all the Red Standards with 5400RPM and 256 cache.
Mixing RPM, the overall speed of the array will be slightly slower.

Will it work? Probably, yes.

I previously had a RAID 5 of 2 different type Seagates and a Toshiba.
2x 7200 and 1x 5400.

I've since gone completely away from RAID 5.
 
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liberty610

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Mixing RPM, the overall speed of the array will be slightly slower.

Will it work? Probably, yes.

I previously had a RAID 5 of 2 different type Seagates and a Toshiba.
2x 7200 and 1x 5400.

I've since gone completely away from RAID 5.
The PR4100 only offers RAID 0, 1, 10, 5, JBOD. I used Raid 5 for the mix of redundancy and speed.
 

liberty610

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You were asked -

not total capacity of all the drives combined.
And my reply was "There is quite a bit on it. It's a 32TB total (4 drives of 8TB) and there is roughly only 11TB free. "

This not only provided information about what sizes the disks where, but also provided the information that I was using a large amount of the array, but still had some free space.

Now are you going to continue to split hairs on irrelevant portions of this topic, or can we move on?
 
And my reply was "There is quite a bit on it. It's a 32TB total (4 drives of 8TB) and there is roughly only 11TB free. "
This not only provided information about what sizes the disks where, but also provided the information that I was using a large amount of the array, but still had some free space.
Now are you going to continue to split hairs on irrelevant portions of this topic, or can we move on?
But we still don't know, how much data is on the array.
Is it 4*7.27 - 11 = 18GB ?
or is it 22 - 11 = 11GB ?

If it is 18GB, then you don't have RAID 5 array and your data is not recoverable.

This "hairsplitting" is necessary to determine, if you can be helped at all.
IMHO - a very reasonable question to be asked.
 
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