RAID Capacity Expansion

I started out with a diskless EX4 and added disks one-by-one (trying to simulate the general use case where people buy drives only when they want to expand capacity):

With one disk, I could initialize a JBOD volume. After adding a second disk - I could change to RAID-1 without loss of existing data. I added a third disk - migrated to RAID-5 without data loss. Now, after adding the 4th disk – I found that
I was given an option to change to RAID-5 (I was already in RAID-5 with 3 disks) – but this required all disks to be formatted again. I couldn’t find a way to expand from 3 disks to 4 while remaining in RAID-5 and keeping existing data intact.

Is this feature (online RAID capacity expansion) available in the firmware? If so, where do I find that option in the UI? If not, I find it really strange that there are a number of advanced features (for example, Thecus doesn’t allow single disk JBOD to RAID-1 migration in their NAS units, but WD allows that in the EX4), but this seemingly straightforward (and often taken for granted) feature is missing.

Other minor complaints I have are:

  1. Fan speed seems to top out at 1035 rpm. During RAID-1 to RAID-5 migration with WD RE drives, I found HDD temperatures reaching 58 - 60 C. Any reasons not to go in for a better fan, given that we have variable fan speed control? (I have to say the fan is pretty quiet)

  2. There is no option to view detailed logs. For example, I want to know when disk rebuild starts (I see that the Notification list gives some basic info like when a new disk gets inserted or when volume rebuilding completes, but information like when volume resizing started and finished is not available). I also checked under /var/log , but couldn’t find the necessary information in any of the files.

  3. The NAS seems to be running some sort of scraper in the background which might affect NAS performance (I see it does take up a lot of CPU cycles). I have to see the difference in performance with the media server enabled and disabled to see how bad the effect is.

I’ll recommend you to contact WD Support for this case.

WD Contact info:

Hi Ganesh,

I would be interested in knowing what your findings were, if you were able to correspond with the support and had time to come to some type of conclusion on these points raised in your original post.


Yes, got answers for two questions:

  1. RAID expansion:

We currently support three RAID migration modes:
1. JBOD to RAID 1
2. JBOD to RAID 5
3. RAID 1 to RAID 5
With the online raid migration, we do not support that yet. This is scheduled to be released in a firmware update in late January.

  1. Fan speeds:

Our MAX RPM for the fan is 2400RPM.
There are four different fan states (low, medium, high and max), depending on the system temperature the fan will spin according to its preset rpm.
State 1: ~900rpm
State 2: ~1400rpm
State 3: ~1900rpm
State 4: ~2400rpm
When the WD RE drives temperature is at 58-59degC, the fan state is between low and medium state, which is between 900 and 1400rpm.

We do not want to run the fan at high speed as it will cause a couple issues:

1. Stretch the fan rpm that might reduce the lifespan of the fan
2. Create unnecessary acoustic noise

There is no issue with the drives running at that temperature.

Thanks for your update.

Is RAID 5 the appropriate and optimal setup for a home environment with 4 2TB drives installed?

Yes.  youd never realize the speeds of raid 10 via gigabit only double protection.   Raid 0 gigabit bottleneck and no redundancy.  raid 1 super paranoid same data on the ALL four drives.  

RAID 5 would give you capacity, protection, and read speed reading from 3 drives in a stripe.  .