Readynas 104 - Drive replacement / drive addition

BLUF: Purchased 2 new WD Red 3tb Drives (WD30EFRX) to add to my existing 3x 1tb Drives. Which drive do I remove and in which order? Add the 4th and wait add and remove?

So that Bottom Line up Front should give you an idea of what im asking, I did some searches on how to add drives or replace drives, but since I only have 3 drives in my 104 I just want to make sure Im doing it correctly.

I purchased this ReadyNAS to get some data redundancy on my network (media etc), so I am using my old workstation drives in the NAS (I know bad idea, but I already built the array before researching).

Here are the drives and their SMART specs:

Model Family:     Western Digital Caviar Green
Device Model:     WDC WD10EADS-11M2B1
SMART Attributes Data Structure revision number: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x002f   200   170   051    Pre-fail  Always       -       0
  3 Spin_Up_Time            0x0027   124   107   021    Pre-fail  Always       -       6800
  4 Start_Stop_Count        0x0032   055   055   000    Old_age   Always       -       45074
  5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x002e   100   253   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   052   052   000    Old_age   Always       -       35631
 10 Spin_Retry_Count        0x0032   100   100   000    Old_age   Always       -       0
 11 Calibration_Retry_Count 0x0032   100   100   000    Old_age   Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       517
192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       229
193 Load_Cycle_Count        0x0032   180   180   000    Old_age   Always       -       61742
194 Temperature_Celsius     0x0022   104   089   000    Old_age   Always       -       43
196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0030   200   200   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       0
200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       0

Model Family:     Western Digital Caviar Green (AF)
Device Model:     WDC WD10EARS-00Y5B1
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x002f   200   200   051    Pre-fail  Always       -       0
  3 Spin_Up_Time            0x0027   191   185   021    Pre-fail  Always       -       6441
  4 Start_Stop_Count        0x0032   094   094   000    Old_age   Always       -       6277
  5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x002e   100   253   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   062   062   000    Old_age   Always       -       28299
 10 Spin_Retry_Count        0x0032   100   100   000    Old_age   Always       -       0
 11 Calibration_Retry_Count 0x0032   100   100   000    Old_age   Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       514
192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       351
193 Load_Cycle_Count        0x0032   038   038   000    Old_age   Always       -       487882
194 Temperature_Celsius     0x0022   101   098   000    Old_age   Always       -       46
196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0030   200   200   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       0
200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       0

Model Family:     Western Digital Black
Device Model:     WDC WD1002FAEX-00Y9A0
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x002f   200   200   051    Pre-fail  Always       -       21
  3 Spin_Up_Time            0x0027   174   171   021    Pre-fail  Always       -       4291
  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       991
  5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x002e   100   253   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   065   064   000    Old_age   Always       -       26270
 10 Spin_Retry_Count        0x0032   100   100   000    Old_age   Always       -       0
 11 Calibration_Retry_Count 0x0032   100   100   000    Old_age   Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       507
192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       240
193 Load_Cycle_Count        0x0032   200   200   000    Old_age   Always       -       750
194 Temperature_Celsius     0x0022   101   092   000    Old_age   Always       -       46
196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0030   200   200   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       0
200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       0

Drive Usage

Filesystem      1K-blocks      Used Available Use% Mounted on
/dev/md127     1943821568 997890704 944950192  52% /data

So As you can see I have two greens and a black WD drives, I have tried to decide if its most risky to keep the black in their or pull the black.

Let me know team!

I appreciate the asistance.