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Pruebas con librerías de cintas sobre servidores Linux

En este post mostraré algunos comandos para operar con una librería de cintas desde el sistema operativo. Pueden ser útiles para la verificación de una correcta instalación o como herramientas de diagnóstico en caso de errores de operación observados desde la plataforma de backup. Para este ejemplo el software de backup es Netbackup , librería Dell ML4000 con drives IBM Ultrium 4 y Sistema Operativo Red Hat Linux 5. Las operaciones de prueba son las siguientes:

– Existencia del dispositivo de control de la librería en el sistema operativo despues de realizar las zonas correspondientes en los switches de fibra. Si el sistema operativo ha reconocido la lun de control de la librería debe de aparecer un nuevo dispositivo tipo /dev/stX:

mediabackup01.root./root # ls /dev/st*
/dev/st0  /dev/st0a  /dev/st0l  /dev/st0m  /dev/stderr  /dev/stdin  /dev/stdout

Para conocer modo de operación de la librería y el driver st para dispositivos de cintas con acceso secuencial ver:

http://linux.about.com/library/cmd/blcmdl4_st.htm

– Existencia de los dispositivos drives de cintas en el sistema operativo tipo /dev/nstX:

mediabackup01.root./root # ls /dev/nst*
nst0   nst0a  nst0l  nst0m  nst1   nst1a  nst1l  nst1m

Para conocer los modos de operación de cada dispositivo ver para mas referencias:

http://linux.about.com/library/cmd/blcmdl4_st.htm

http://es.tldp.org/NuLies/web/2.2/Documentation/devices.txt

        	Dispositivos de cinta SCSI
		  0 = /dev/st0		Primera cinta SCSI, modo 0
		  1 = /dev/st1		Segunda cinta SCSI, mode 0
		      ...
		 32 = /dev/st0l		Primera cinta SCSI, modo 1
		 33 = /dev/st1l		Segunda cinta SCSI, modo 1
		      ...
		 64 = /dev/st0m		Primera cinta SCSI, modo 2
		 65 = /dev/st1m		Segunda cinta SCSI, modo 2
		      ...
		 96 = /dev/st0a		Primera cinta SCSI, modo 3
		 97 = /dev/st1a		Segunda cinta SCSI, modo 3
		      ...
		128 = /dev/nst0		Primera cinta SCSI, modo 0, sin rebobinado
		129 = /dev/nst1		Segunda cinta SCSI, modo 0, sin rebobinado
		      ...
		160 = /dev/nst0l	Primera cinta SCSI, modo 1, sin rebobinado
		161 = /dev/nst1l	Segunda cinta SCSI, modo 1, sin rebobinado
		      ...
		192 = /dev/nst0m	Primera cinta SCSI, modo 2, sin rebobinado
		193 = /dev/nst1m	Segunda cinta SCSI, modo 2, sin rebobinado
		      ...
		224 = /dev/nst0a	Primera cinta SCSI, modo 3, sin rebobinado
		225 = /dev/nst1a	Segunda cinta SCSI, modo 3, sin rebobinado
		      ...

		"Sin rebobinado" se refiere a la no realización del rebobinado automático
		efectuado por defecto al cerrar el dispositivo. Las funciones
		MTREW o MTOFFL de ioctl() pueden utilizarse para rebobinar
		la cinta sin importar qué dispositivo se utiliza para acceder a él.

En el caso de que no aparezca el dispositivo st o nst, mirar en los módulos del kernel cargados si aparecen los drivers correspondientes (lsmod),  revisar el zoneado en los switches de fibra, usar herramientas de las HBAs para estudio  de dispositivos en la SAN (tipo Sansurfer para HBAs Qlogic o OneCommand para HBAs Emulex) . En ocasiones, por tipo o parametrización de HBAs puede ser necesario reiniciar el servidor con el fin que reconozca los nuevos dispositivos presentados por fibra. Hay fabricantes que aconsejan instalar drivers propietarios en vez de usar los drivers nativos del sistema operativo requiriendo una consulta a soporte para obtenerlos …

– Pruebas de operaciones sobre la librería: consultas del inventario de la librería, movimiento de cintas entre stots, montaje y desmontaje en un drive.  Pueden usarse los comando nativos de linux mt/dd y/o la herramienta propia de Netbackup robtest.

Un ejemplo con robtest puede ser:

mediabackup01.root./etc # robtest
Configured robots with local control supporting test utilities:
  TLD(0)     robotic path = /dev/sg14
Robot Selection
---------------
  1)  TLD 0
  2)  none/quit
Enter choice:
Enter choice: 1
Robot selected: TLD(0)   robotic path = /dev/sg14
Invoking robotic test utility:
/usr/openv/volmgr/bin/tldtest -rn 0 -r /dev/sg14
Opening /dev/sg14
MODE_SENSE complete
Enter tld commands (? returns help information)
m d2 s11 "-- mueve cinta de drive 2 a slot 11"
Initiating MOVE_MEDIUM from address 257 to 4106
s d "-- muestra dispositivos drives de cintas en la librería"
MOVE_MEDIUM complete
drive 1 (addr 256) access = 1 Contains Cartridge = no
drive 2 (addr 257) access = 1 Contains Cartridge = no
READ_ELEMENT_STATUS complete
s s "-- muestra un inventario de cintas de la librería"
slot 1 (addr 4096) contains Cartridge = yes
Source address = 4096
Barcode = A00113L4
slot 2 (addr 4097) contains Cartridge = no
slot 3 (addr 4098) contains Cartridge = yes
Source address = 4098
Barcode = 000415L4
slot 4 (addr 4099) contains Cartridge = yes
Source address = 4099
Barcode = A00128L4
slot 5 (addr 4100) contains Cartridge = yes
Source address = 4100
Barcode = 000425L4
slot 6 (addr 4101) contains Cartridge = yes
Source address = 4101
Barcode = A00099L4
slot 7 (addr 4102) contains Cartridge = yes
Source address = 4102
Barcode = A00014L4
slot 8 (addr 4103) contains Cartridge = yes
Source address = 4103
Barcode = 000394L4
<< Press return to continue, or q and return to stop >>
m s1 d2 "-- Mueve cinta del slot 1 al drive 2."
Initiating MOVE_MEDIUM from address 4096 to 257
MOVE_MEDIUM complete

-Prueba de escritura en drive: Un ejemplo de escritura en drive con la herramienta dd del sistema operativo después de montar una cinta en el drive  /dev/nst0 :

mediabackup01.root./etc # tar cvf etc.tar /etc
mediabackup01.root./etc # dd if=/etc/etc.tar of=/dev/nst0
533700+0 records in
533700+0 records out
273254400 bytes (273 MB) copied, 54.2875 seconds, 5.0 MB/s

Nota: Se puede usar la utilidad mtx al igual que robtest. Hay un ejemplo del uso de mtx en entorno Windows al final del siguiente post:

http://www.almacenamientoabierto.com/2010/07/vtl-4-creando-una-vtl-open-source-sobre-fcp-fibra-optica/

 

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