MongoDB 5.0 Installation Fails on CPUs Without AVX Support and How to Fix It

MongoDB 5.0 was released with new core features such as time‑series collections, but on some older servers the binaries may crash if the CPU does not support the AVX instruction set.

Phenomenon

On a CentOS 7.2 system, after installing the mongodb-5.0.x package, running mongo or mongod immediately returns:

[root@10-186-61-38 mongodb]# ./mongo --help
Illegal instruction
[root@10-186-61-38 bin]# ./mongod --help
Illegal instruction

The same commands work without issue on MongoDB 4.4.9.

[root@10-186-61-38 bin]# ./mongo --help
MongoDB shell version v4.4.9
usage: ./mongo [options] [db address] [file names (ending in .js)]

Investigation

Running dmesg -T shows two "invalid opcode" traps:

[Thu Dec 23 18:05:13 2021] traps: mongo[16596] trap invalid opcode ip:7f0ad9fa90da sp:7ffe9deaa050 error:0 in mongo[7f0ad7f86000+2c8c000]
[Thu Dec 23 18:05:17 2021] traps: mongod[16597] trap invalid opcode ip:7f3b1e329a6a sp:7ffc8fb540e0 error:0 in mongod[7f3b1a355000+5110000]

The error is caused by the CPU lacking the AVX instruction set required by MongoDB 5.0.

Official MongoDB documentation states that MongoDB 5.0 requires a CPU that supports AVX. The requirement is not mentioned for earlier versions.

Checking the server’s CPU flags confirms the absence of the "avx" flag:

[root@10-186-61-38 ~]# cat /proc/cpuinfo
processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 13
model name  : QEMU Virtual CPU version 2.5+
flags       : fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pse36 clflush mmx fxsr sse sse2 syscall nx lm rep_good nopl xtopology eagerfpu pni cx16 x2apic hypervisor lahf_lm

AVX‑Capable CPU Test

Running the same commands on a server whose CPU supports AVX works correctly, confirming that the issue is hardware‑related.

What Is AVX?

AVX (Advanced Vector Extensions) is an x86 instruction‑set extension introduced by Intel in 2008 and first supported in the Sandy Bridge processors. AMD added support in the Bulldozer series. AVX widens SIMD registers from 128 bits (XMM) to 256 bits (YMM), potentially doubling floating‑point throughput.

MongoDB’s release notes hint that the WiredTiger storage engine in 5.0 uses AVX‑optimized memcpy routines, which can increase read throughput by up to 63 %.

Conclusion

Before installing or upgrading to MongoDB 5.0, verify that the server’s CPU supports AVX. The simplest check is:

grep avx /proc/cpuinfo

If the command returns no results, the CPU lacks AVX and MongoDB 5.0 cannot run.

References

MongoDB community forum discussion

MongoDB Production Notes

Getting storage engines ready for fast storage devices (mentions AVX optimizations)