ib_write_bw_postlist: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/ib_write_bw_postlist - from package: perftest

You may install the required package with command yum install {package}
Error in other languages:
ib_write_bw_postlist: bevel nie gevind nie
ib_write_bw_postlist: comandă negăsită
ib_write_bw_postlist: comando não encontrado
ib_write_bw_postlist: commande introuvable
ib_write_bw_postlist: command not found
ib_write_bw_postlist: käsku ei ole
ib_write_bw_postlist: không tìm thấy lệnh
ib_write_bw_postlist: komanda nerasta
ib_write_bw_postlist: Kommando nicht gefunden.
ib_write_bw_postlist: kommandot finns inte
ib_write_bw_postlist: komut yok
ib_write_bw_postlist: nie znaleziono polecenia
ib_write_bw_postlist: níor aimsíodh an t-ordú
ib_write_bw_postlist: no se encontró la orden
ib_write_bw_postlist: no s'ha trobat l'ordre
ib_write_bw_postlist: opdracht niet gevonden
ib_write_bw_postlist: parancs nem található
ib_write_bw_postlist: perintah tidak ditemukan
ib_write_bw_postlist: príkaz nenájdený
ib_write_bw_postlist: příkaz nenalezen
ib_write_bw_postlist: команда не найдена
ib_write_bw_postlist: командата не е открита
ib_write_bw_postlist: 命令找不到
ib_write_bw_postlist: コマンドが見つかりません