dm-cache setup for big GPT iSCSI partitions

[vco...@gmail.com]

Hi all, and congratulation for this great project!

I'm using dm-cache released into 3.9.6 kernel on a Centos 6.3 Linux distro.
I've attached a QNAP 12TB iScsi NAS with 2 LUN's:

scsi6 : iSCSI Initiator over TCP/IP
scsi 6:0:0:0: Direct-Access     QNAP     iSCSI Storage    3.1  PQ: 0 ANSI: 5
sd 6:0:0:0: Attached scsi generic sg1 type 0
sd 6:0:0:0: [sdb] 10588520448 512-byte logical blocks: (5.42 TB/4.93 TiB)
scsi 6:0:0:1: Direct-Access     QNAP     iSCSI Storage    3.1  PQ: 0 ANSI: 5
sd 6:0:0:1: Attached scsi generic sg2 type 0
sd 6:0:0:1: [sdc] 10622074880 512-byte logical blocks: (5.43 TB/4.94 TiB)
sd 6:0:0:0: [sdb] Write Protect is off
sd 6:0:0:0: [sdb] Mode Sense: 2f 00 00 00
sd 6:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
sd 6:0:0:1: [sdc] Write Protect is off
sd 6:0:0:1: [sdc] Mode Sense: 2f 00 00 00
sd 6:0:0:1: [sdc] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
 sdb: sdb1
 sdc: sdc1
sd 6:0:0:0: [sdb] Attached SCSI disk
sd 6:0:0:1: [sdc] Attached SCSI disk

Using parted I've created a GPT partition:
[root@localhost ~]# parted /dev/sdb print
Modello: QNAP iSCSI Storage (scsi)
Disco /dev/sdb: 5421GB
Dimensione del settore (logica/fisica): 512B/512B
Tabella delle partizioni: gpt

Numero  Inizio  Fine    Dimensione  File system  Nome     Flag
 1      1049kB  5421GB  5421GB      reiserfs     primary


[root@localhost ~]# fdisk /dev/sdb

WARNING: GPT (GUID Partition Table) detected on '/dev/sdb'! The util fdisk doesn't support GPT. Use GNU Parted.


WARNING: The size of this disk is 5.4 TB (5421322469376 bytes).
DOS partition table format can not be used on drives for volumes
larger than (2199023255040 bytes) for 512-byte sectors. Use parted(1) and GUID
partition table format (GPT).


WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

Comando (m per richiamare la guida): p

Disco /dev/sdb: 5421.3 GB, 5421322469376 byte

255 testine, 63 settori/tracce, 659104 cilindri
Unità = cilindri di 16065 * 512 = 8225280 byte
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 262144 bytes
Identificativo disco: 0x00000000

Dispositivo Boot      Start         End      Blocks   Id  System
/dev/sdb1               1      267350  2147483647+  ee  GPT

Comando (m per richiamare la guida): q


[root@localhost ~]# blockdev --getsz /dev/sdb
10588520448

Now i'm using local sata disk for metadata and cache storage

[root@localhost ~]# fdisk /dev/sda -l

Disco /dev/sda: 500.1 GB, 500107862016 byte

255 testine, 63 settori/tracce, 60801 cilindri
Unità = cilindri di 16065 * 512 = 8225280 byte
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Identificativo disco: 0x0008fdda

Dispositivo Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      102400   83  Linux
La partizione 1 non termina al limite del cilindro.
/dev/sda2              13         141     1024000   83  Linux
La partizione 2 non termina al limite del cilindro.
/dev/sda3             141         396     2048000   83  Linux
La partizione 3 non termina al limite del cilindro.
/dev/sda4             396       60802   485211136    5  Esteso
/dev/sda5             396         651     2048000   83  Linux
/dev/sda6             651         779     1024000   82  Linux swap / Solaris
/dev/sda7             779         906     1024000   83  Linux
/dev/sda8             906       40000   314025472+  83  Linux
/dev/sda9           40001       41000     8032468+  83  Linux
/dev/sda10          41001       60802   159054028+  83  Linux

And formatted all reiserfs partitions sda9 (8GByte) for metadata, sda10 (160Gbytes) for cache and sdb1 5Tbyte for origin data disk.
Using the command:

[root@localhost ~]# dmsetup create dati1 --table '0 10588520448 cache /dev/sda9 /dev/sda10 /dev/sdb1 2048 1 writethrough default 0'
device-mapper: reload ioctl on dati1 failed: Invalid argument

Command failed with dmesg message:
Jun 19 09:18:57 localhost kernel: device-mapper: table: 253:0: cache: Device size larger than cached device
Jun 19 09:18:57 localhost kernel: device-mapper: ioctl: error adding target to table

Where i'm wrong?
Thanks for all your work.
Greetings
Vito

[Gregory Jean-baptise]

It would appear that you are using the kernel built-in dm-cache, which is different from our dm-cache and is not based on our code. I would advise reading this article and then asking again in the appropriate channels.

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Gregory Jean-Baptiste

Undergraduate Research Assistant @ V.I.S.A

Florida International University