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after upgrading a server from centos 4 to centos 6, only 8 out of 12 Gb are available to the system; I thought some were faulty but it's not the case (i tried to swith memory with another server) I have 6 x 2GB DDR DIMM;

free
             total       used       free     shared    buffers     cached
Mem:       8195024     560508    7634516          0      37388     169116
-/+ buffers/cache:     354004    7841020
Swap:      4200956          0    4200956

and/proc/meminfo

cat /proc/meminfo
MemTotal:        8195024 kB
MemFree:         7702732 kB
Buffers:           29232 kB
Cached:           106368 kB
SwapCached:            0 kB
Active:            93684 kB
Inactive:         107164 kB
Active(anon):      65476 kB
Inactive(anon):     1032 kB
Active(file):      28208 kB
Inactive(file):   106132 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       4200956 kB
SwapFree:        4200956 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:         65244 kB
Mapped:            33532 kB
Shmem:              1264 kB
Slab:             211304 kB
SReclaimable:      24852 kB
SUnreclaim:       186452 kB
KernelStack:        1960 kB
PageTables:        11336 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     8298468 kB
Committed_AS:     346860 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      321300 kB
VmallocChunk:   34359408376 kB
HardwareCorrupted:     0 kB
AnonHugePages:      8192 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:       10176 kB
DirectMap2M:     8378368 kB

Here are some outputs:

dmidecode -t 17
#dmidecode 2.10
SMBIOS 2.3 present.

Handle 0x003A, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0039
Error Information Handle: Not Provided
Total Width: 144 bits
Data Width: 128 bits
Size: 2048 MB
Form Factor: DIMM
Set: None
Locator: A0
Bank Locator: Bank0/1
Type: DDR
Type Detail: Synchronous
Speed: 400 MHz
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

Handle 0x003B, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0039
Error Information Handle: Not Provided
Total Width: 144 bits
Data Width: 128 bits
Size: 2048 MB
Form Factor: DIMM
Set: None
Locator: A1
Bank Locator: Bank2/3
Type: DDR
Type Detail: Synchronous
Speed: 400 MHz
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

Handle 0x003C, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0039
Error Information Handle: Not Provided
Total Width: 144 bits
Data Width: 128 bits
Size: 2048 MB
Form Factor: DIMM
Set: None
Locator: A2
Bank Locator: Bank4/5
Type: DDR
Type Detail: Synchronous
Speed: 400 MHz
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

Handle 0x003D, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0039
Error Information Handle: Not Provided
Total Width: 144 bits
Data Width: 128 bits
Size: 2048 MB
Form Factor: DIMM
Set: None
Locator: A3
Bank Locator: Bank6/7
Type: DDR
Type Detail: Synchronous
Speed: 400 MHz
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

Handle 0x003E, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0039
Error Information Handle: Not Provided
Total Width: 144 bits
Data Width: 128 bits
Size: 16384 MB
Form Factor: DIMM
Set: None
Locator: A4
Bank Locator: Bank8/9
Type: DDR
Type Detail: Synchronous
Speed: 400 MHz
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

Handle 0x003F, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0039
Error Information Handle: Not Provided
Total Width: 144 bits
Data Width: 128 bits
Size: 16384 MB
Form Factor: DIMM
Set: None
Locator: A5
Bank Locator: Bank10/11
Type: DDR
Type Detail: Synchronous
Speed: 400 MHz
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

The last two show up as 16384MB, which should be 2048MB

I also setup lm_sensors + i2c-tools:

decode-dimms
# decode-dimms version 5929 (2011-02-16 14:58:38 +0100)

Memory Serial Presence Detect Decoder
By Philip Edelbrock, Christian Zuckschwerdt, Burkart Lingner,
Jean Delvare, Trent Piepho and others


Decoding EEPROM: /sys/bus/i2c/drivers/eeprom/2-0050
Guessing DIMM is in                             bank 1

---=== SPD EEPROM Information ===---
EEPROM Checksum of bytes 0-62                   OK (0xE2)
# of bytes written to SDRAM EEPROM              128
Total number of bytes in EEPROM                 256
Fundamental Memory type                         DDR SDRAM
SPD Revision                                    1.0

---=== Memory Characteristics ===---
Maximum module speed                            400MHz (PC3200)
Size                                            2048 MB
Voltage Interface Level                         SSTL 2.5V
Module Configuration Type                       ECC
Refresh Rate                                    Reduced (7.8 us) - Self Refresh
tCL-tRCD-tRP-tRAS                               3-3-3-8
Supported CAS Latencies                         3T, 2.5T, 2T
Supported CS Latencies                          0
Supported WE Latencies                          1
Minimum Cycle Time                              5 ns at CAS 3
                                                6 ns at CAS 2.5
                                                7.5 ns at CAS 2
Maximum Access Time                             0.5 ns at CAS 3
                                                0.5 ns at CAS 2.5
                                                0.5 ns at CAS 2
Module Height                                   1.125" to 1.25"

---=== Manufacturing Information ===---
Manufacturer                                    Infineon (former Siemens)
Manufacturing Location Code                     V
Part Number                                     72D256220GBR5B    
Revision Code                                   0x030C
Manufacturing Date                              2006-W01
Assembly Serial Number                          0x0600C212


Decoding EEPROM: /sys/bus/i2c/drivers/eeprom/2-0051
Guessing DIMM is in                             bank 2

---=== SPD EEPROM Information ===---
EEPROM Checksum of bytes 0-62                   OK (0xB5)
# of bytes written to SDRAM EEPROM              128
Total number of bytes in EEPROM                 256
Fundamental Memory type                         DDR SDRAM
SPD Revision                                    1.0

---=== Memory Characteristics ===---
Maximum module speed                            400MHz (PC3200)
Size                                            2048 MB
Voltage Interface Level                         SSTL 2.5V
Module Configuration Type                       ECC
Refresh Rate                                    Reduced (7.8 us) - Self Refresh
tCL-tRCD-tRP-tRAS                               3-3-3-8
Supported CAS Latencies                         3T, 2.5T
Supported CS Latencies                          0
Supported WE Latencies                          1
Minimum Cycle Time                              5 ns at CAS 3
                                                6 ns at CAS 2.5
Maximum Access Time                             0.65 ns at CAS 3
                                                0.7 ns at CAS 2.5

---=== Manufacturing Information ===---
Manufacturer                                    Kingston
Manufacturing Location Code                     0x04
Part Number                                     Undefined
Manufacturing Date                              2006-W14
Assembly Serial Number                          0x08108AB0


Decoding EEPROM: /sys/bus/i2c/drivers/eeprom/2-0052
Guessing DIMM is in                             bank 3

---=== SPD EEPROM Information ===---
EEPROM Checksum of bytes 0-62                   OK (0xE2)
# of bytes written to SDRAM EEPROM              128
Total number of bytes in EEPROM                 256
Fundamental Memory type                         DDR SDRAM
SPD Revision                                    1.0

---=== Memory Characteristics ===---
Maximum module speed                            400MHz (PC3200)
Size                                            2048 MB
Voltage Interface Level                         SSTL 2.5V
Module Configuration Type                       ECC
Refresh Rate                                    Reduced (7.8 us) - Self Refresh
tCL-tRCD-tRP-tRAS                               3-3-3-8
Supported CAS Latencies                         3T, 2.5T, 2T
Supported CS Latencies                          0
Supported WE Latencies                          1
Minimum Cycle Time                              5 ns at CAS 3
                                                6 ns at CAS 2.5
                                                7.5 ns at CAS 2
Maximum Access Time                             0.5 ns at CAS 3
                                                0.5 ns at CAS 2.5
                                                0.5 ns at CAS 2
Module Height                                   1.125" to 1.25"

---=== Manufacturing Information ===---
Manufacturer                                    Infineon (former Siemens)
Manufacturing Location Code                     V
Part Number                                     72D256220GBR5B    
Revision Code                                   0x030C
Manufacturing Date                              2006-W01
Assembly Serial Number                          0x0600AE27


Decoding EEPROM: /sys/bus/i2c/drivers/eeprom/2-0053
Guessing DIMM is in                             bank 4

---=== SPD EEPROM Information ===---
EEPROM Checksum of bytes 0-62                   OK (0xB5)
# of bytes written to SDRAM EEPROM              128
Total number of bytes in EEPROM                 256
Fundamental Memory type                         DDR SDRAM
SPD Revision                                    1.0

---=== Memory Characteristics ===---
Maximum module speed                            400MHz (PC3200)
Size                                            2048 MB
Voltage Interface Level                         SSTL 2.5V
Module Configuration Type                       ECC
Refresh Rate                                    Reduced (7.8 us) - Self Refresh
tCL-tRCD-tRP-tRAS                               3-3-3-8
Supported CAS Latencies                         3T, 2.5T
Supported CS Latencies                          0
Supported WE Latencies                          1
Minimum Cycle Time                              5 ns at CAS 3
                                                6 ns at CAS 2.5
Maximum Access Time                             0.65 ns at CAS 3
                                                0.7 ns at CAS 2.5

---=== Manufacturing Information ===---
Manufacturer                                    Kingston
Manufacturing Location Code                     0x04
Part Number                                     Undefined
Manufacturing Date                              2006-W14
Assembly Serial Number                          0x011046B4


Decoding EEPROM: /sys/bus/i2c/drivers/eeprom/2-0054
Guessing DIMM is in                             bank 5

---=== SPD EEPROM Information ===---
EEPROM Checksum of bytes 0-62                   OK (0xE2)
# of bytes written to SDRAM EEPROM              128
Total number of bytes in EEPROM                 256
Fundamental Memory type                         DDR SDRAM
SPD Revision                                    1.0

---=== Memory Characteristics ===---
Maximum module speed                            400MHz (PC3200)
Size                                            2048 MB
Voltage Interface Level                         SSTL 2.5V
Module Configuration Type                       ECC
Refresh Rate                                    Reduced (7.8 us) - Self Refresh
tCL-tRCD-tRP-tRAS                               3-3-3-8
Supported CAS Latencies                         3T, 2.5T, 2T
Supported CS Latencies                          0
Supported WE Latencies                          1
Minimum Cycle Time                              5 ns at CAS 3
                                                6 ns at CAS 2.5
                                                7.5 ns at CAS 2
Maximum Access Time                             0.5 ns at CAS 3
                                                0.5 ns at CAS 2.5
                                                0.5 ns at CAS 2
Module Height                                   1.125" to 1.25"

---=== Manufacturing Information ===---
Manufacturer                                    Infineon (former Siemens)
Manufacturing Location Code                     V
Part Number                                     72D256220GBR5B    
Revision Code                                   0x030C
Manufacturing Date                              2006-W01
Assembly Serial Number                          0x04048112


Decoding EEPROM: /sys/bus/i2c/drivers/eeprom/2-0055
Guessing DIMM is in                             bank 6

---=== SPD EEPROM Information ===---
EEPROM Checksum of bytes 0-62                   OK (0xE2)
# of bytes written to SDRAM EEPROM              128
Total number of bytes in EEPROM                 256
Fundamental Memory type                         DDR SDRAM
SPD Revision                                    1.0

---=== Memory Characteristics ===---
Maximum module speed                            400MHz (PC3200)
Size                                            2048 MB
Voltage Interface Level                         SSTL 2.5V
Module Configuration Type                       ECC
Refresh Rate                                    Reduced (7.8 us) - Self Refresh
tCL-tRCD-tRP-tRAS                               3-3-3-8
Supported CAS Latencies                         3T, 2.5T, 2T
Supported CS Latencies                          0
Supported WE Latencies                          1
Minimum Cycle Time                              5 ns at CAS 3
                                                6 ns at CAS 2.5
                                                7.5 ns at CAS 2
Maximum Access Time                             0.5 ns at CAS 3
                                                0.5 ns at CAS 2.5
                                                0.5 ns at CAS 2
Module Height                                   1.125" to 1.25"

---=== Manufacturing Information ===---
Manufacturer                                    Infineon (former Siemens)
Manufacturing Location Code                     V
Part Number                                     72D256220GBR5B    
Revision Code                                   0x030C
Manufacturing Date                              2006-W01
Assembly Serial Number                          0x0600BA20


Number of SDRAM DIMMs detected and decoded: 6

Here all have 2048MB and are detected (EEprom checksums of bytes 0-62 are all OK)

I'm gonna launch a memtest for the night

Thanks for any hint

EDIT: of course i'm on 64bits centos:

uname -r
2.6.32-71.el6.x86-64
share|improve this question
    
Was the memory working before the upgrade? Does the memory detect correctly at POST? –  jgoldschrafe Dec 8 '11 at 16:11
1  
Please also show cat /proc/meminfo and free -m. –  Janne Pikkarainen Dec 8 '11 at 16:27
    
Yes, memory was 12GB, and it only shows 8GB at post... Didn't think of checking this, so it's clearly hardware, right? –  Asimo Dec 8 '11 at 16:31
    
I'll check the bios settings then... –  Asimo Dec 8 '11 at 16:38

1 Answer 1

up vote 2 down vote accepted

If it is only showing at 8GB at POST, then it isn't a CentOS problem. Chances are something hardware-related happened during the upgrade coincidentally, or something happened a while ago and you didn't notice.

You should check to make sure that you're running the latest BIOS revision for your hardware. If that falls short, you should contact them for support.

share|improve this answer
    
Thanks for your answer; it's strange that the server boots without any beeps, as it should with faulty memory, and that lm_sensors can "see" all of them; I'll investigate bios/hardware –  Asimo Dec 8 '11 at 17:02

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