http://blog.csdn.net/kinges/article/details/40425841
转自：http://blog.csdn.net/kinges/article/details/40425841
主机报错信息：
Buffer I/O errors occurring on SAN devices presented to Linux host using Linux native multipathing.
kernel: Buffer I/O error on device sdb, logical block 0
kernel: Buffer I/O error on device sdb, logical block 1
kernel: Buffer I/O error on device sdb, logical block 2
kernel: Buffer I/O error on device sdb, logical block 3
A server using a LUN, which is presented by a storage array through
fabric channels, may show buffer I/O errors while the server is booting
or commands such as fdisk and vgscan are being run. The access can be a
read or write attempt. These messages are
sometimes harmless. When using PowerPath, these errors are suppressed.
However, in the case where Linux native multipathing is used, there is
no automatic provision for filtering these messages.
The errors can occur when
using an active/passive storage array, such as EMC Clarion series. These
types of SANs contain two storage processors. LUNs are assigned to only
one of the processors at the time of LUN creation.
The LUN can receive I/O only via that one processor. The other
processor is passive; it acts as a backup, ready to receive I/O if the
active controller fails, or if all paths to the LUN via the active
controller fails.
Paths to the LUN going via the passive controller are passive paths and
will generate an I/O errors should I/O be sent over them. At bootup, the
kernel's SCSI mid-layer scans all paths to find devices. Thus it will
scan both active and passive paths and will
generate buffer I/O errors for the passive paths.
This is a normal behavior for Linux native multipath, and the errors do
not indicate an array issue. The errors can safely be filtered through
the OS logging configuration or the user can avoid access to native
devices (as opposed to using /dev/mapper devices).
Alternatively, a qualified version of PowerPath may be installed, which
will automatically filter these errors.
