eMLC SSD RAID
Replacing a failed SSD module in a Power 740 eMLC PCI-E SAS adapter under AIX
Initial thoughts
- WARNING: the Power 740 cannot be opened while system is powered on! (It will power off when the lid is opened.) You need a full system shutdown (power off managed system) to be able to change the internal SSD disks or PCI cards.
- Note the following: the location code of the adapter (there is a diagram on the cover of the machine) and the disk (eg. "P1-C1-C4-T1-D1")
- Run rmdev on each device on the RAID adapter (eg. 'rmdev -Rdl sissas2')
- Power down the system, open the cover and remove the adapter. If you have the low profile eMLC adapters, they are found in the slot C2 or C4.
- Identify the disk based on the location code
- You can remove the SSD modules in pairs. First, open the small blue metal lever until it disengages from the small pin (approx 90') then the two small blue plastic levers with the location codes printed on them. Then, pull both SSD modules together from the SATA socket in horizontal direction (approx. 1.5-2 cm). It requires little force. Both modules move together. To access the disk adjacent to the adapter circuit board, remove the outer disk first.
- Replace and re-seat the failing module, then put the adapter back in the PCI-E slot carefully.
Device names
sissasX SAS RAID adapter
hdiskX RAID array
pdiskX physical disk
Procedure
Here we had a 4-disk RAID0 which fell apart when a single pdisk died.
After the replacement, the previous array could not be reassembled, the new pdisk formed a separate new array.
After the dead disk is replaced, this is the state of the pdisks on the sissas2 adapter:
# sissasraidmgr -L -l sissas2------------------------------------------------------------------------Name Resource State Description Size------------------------------------------------------------------------sissas2 FFFFFFFF Available PCIe RAID & SSD SAS Adapter 3Gbhdisk2 00FF0000 Optimal RAID 0 Array 177.8GB pdisk6 00040000 Active SSD Array Member 177.8GB*unknwn* 00FFFFFF Failed RAID 0 Array SN81C171D4 pdisk4 00000000 RWProtected SSD Array Member 177.8GB pdisk5 00010000 RWProtected SSD Array Member 177.8GB pdisk7 00050000 RWProtected SSD Array Member 177.8GB *unknwn* 00040000 Missing Array Member N/ABoth arrays should be deleted.
Adding the disks to the other array is not recommended:
"...performance will not be optimal when using this option, since the included device will not contain parity and the data will not be re-striped"
Delete failed array, using the serial number because the array is missing:
Note that 'SN' is not needed.
# sissasraidmgr -D -l sissas2 -e SN81C171D40940-028 SN81C171D4 is an invalid serial number.# sissasraidmgr -D -l sissas2 -e 81C171D4pdisk4 Definedpdisk5 Definedpdisk7 Defined*unknwn* array with serial number 81C171D4 removed# sissasraidmgr -L -l sissas2 -a0 -j1------------------------------------------------------------------------Name Resource State Description Size------------------------------------------------------------------------sissas2 FFFFFFFF Available PCIe RAID & SSD SAS Adapter 3Gbhdisk2 00FF0000 Optimal RAID 0 Array 177.8GB pdisk6 00040000 Active SSD Array Member 177.8GBpdisk4 00000000 Active SSD Array Candidate 177.8GBpdisk5 00010000 Active SSD Array Candidate 177.8GBpdisk7 00050000 Active SSD Array Candidate 177.8GBDelete new array with the replaced disk:
# sissasraidmgr -D -l sissas2 -d hdisk2hdisk2 deletedpdisk6 Defined# sissasraidmgr -L -l sissas2 -a0 -j1------------------------------------------------------------------------Name Resource State Description Size------------------------------------------------------------------------sissas2 FFFFFFFF Available PCIe RAID & SSD SAS Adapter 3Gbpdisk4 00000000 Active SSD Array Candidate 177.8GBpdisk5 00010000 Active SSD Array Candidate 177.8GBpdisk6 00040000 Active SSD Array Candidate 177.8GBpdisk7 00050000 Active SSD Array Candidate 177.8GBCreate array
-r0 stands for 'RAID 0'
# sissasraidmgr -C -r0 -z 'pdisk4 pdisk5 pdisk6 pdisk7'.# sissasraidmgr -L -l sissas2 -a0 -j1------------------------------------------------------------------------Name Resource State Description Size------------------------------------------------------------------------sissas2 FFFFFFFF Available PCIe RAID & SSD SAS Adapter 3Gbhdisk2 00FF0000 Optimal RAID 0 Array 711.2GB pdisk4 00000000 Active SSD Array Member 177.8GB pdisk5 00010000 Active SSD Array Member 177.8GB pdisk6 00040000 Active SSD Array Member 177.8GB pdisk7 00050000 Active SSD Array Member 177.8GBThat's all!
You can start using the array as a regular PV (here as hdisk2) again.
smitty must DIE!! ;-))
References
sissasraidmgr -h