由于OVZ架构的VPS存在超售的问题，商家分配给我们的内存和他们在购买页面标识的内存并不是一致的。超售是必然的，只不过要看商家的良心，看超售严重不严重了。对于ovz架构的vps可以对内存进行数据写入，看看是否在我们的期望值内。
相关命令：
查看初始内存
free -m
切换至内存目录
cd /dev/shm
进行数据写入，标识 count=100 为写入100M，这里在服务商提供的标识数据内，自行进行数据增长
dd if=/dev/zero of=./memtest bs=1M count=100
完成后，执行删除
rm ./memtest
演示
测试机： 标识内存1G，突发内存1G的OVZ架构机器
[root@LeafRainyK ~]# free -m
total used free shared buffers cached
Mem: 1024 35 988 0 0 14
-/+ buffers/cache: 20 1003
Swap: 1024 0 1024
这里可以看到只使用了35M
然后对内存进行数据写入
[root@LeafRainyK shm]# dd if=/dev/zero of=./memtest bs=1M count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 0.0277696 seconds, 3.8 GB/s
[root@LeafRainyK shm]# free -m
total used free shared buffers cached
Mem: 1024 135 888 0 0 14
-/+ buffers/cache: 120 903
Swap: 1024 0 1024
[root@LeafRainyK shm]# dd if=/dev/zero of=./memtest bs=1M count=200
200+0 records in
200+0 records out
209715200 bytes (210 MB) copied, 0.0550656 seconds, 3.8 GB/s
[root@LeafRainyK shm]# free -m
total used free shared buffers cached
Mem: 1024 235 788 0 0 14
-/+ buffers/cache: 220 803
Swap: 1024 0 1024
[root@LeafRainyK shm]# dd if=/dev/zero of=./memtest bs=1M count=300
300+0 records in
300+0 records out
314572800 bytes (315 MB) copied, 0.0824703 seconds, 3.8 GB/s
[root@LeafRainyK shm]# free -m
total used free shared buffers cached
Mem: 1024 335 688 0 0 14
-/+ buffers/cache: 320 703
Swap: 1024 0 1024
[root@LeafRainyK shm]# dd if=/dev/zero of=./memtest bs=1M count=400
400+0 records in
400+0 records out
419430400 bytes (419 MB) copied, 0.111988 seconds, 3.7 GB/s
[root@LeafRainyK shm]# free -m
total used free shared buffers cached
Mem: 1024 435 588 0 0 14
-/+ buffers/cache: 420 603
Swap: 1024 0 1024
[root@LeafRainyK shm]# dd if=/dev/zero of=./memtest bs=1M count=500
500+0 records in
500+0 records out
524288000 bytes (524 MB) copied, 0.139541 seconds, 3.8 GB/s
[root@LeafRainyK shm]# free -m
total used free shared buffers cached
Mem: 1024 532 491 0 0 14
-/+ buffers/cache: 517 506
Swap: 1024 2 1021
[root@LeafRainyK shm]# dd if=/dev/zero of=./memtest bs=1M count=600
dd: writing `./memtest': No space left on device
512+0 records in
511+0 records out
536866816 bytes (537 MB) copied, 0.146447 seconds, 3.7 GB/s
[root@LeafRainyK shm]# free -m
total used free shared buffers cached
Mem: 1024 544 479 0 0 14
-/+ buffers/cache: 529 494
Swap: 1024 2 1021
[root@LeafRainyK shm]# dd if=/dev/zero of=./memtest bs=1M count=700
dd: writing `./memtest': No space left on device
512+0 records in
511+0 records out
536866816 bytes (537 MB) copied, 0.142527 seconds, 3.8 GB/s
[root@LeafRainyK shm]# free -m
total used free shared buffers cached
Mem: 1024 543 480 0 0 14
-/+ buffers/cache: 528 495
Swap: 1024 3 1020
[root@LeafRainyK shm]#
转自blog.gt520.com