RAID Limits

jtl60047 · 08-21-2004, 09:56 AM

Does anyone know if there are any limits to the volume or size of a RAID array that can be supported by LINUX on a single raid card?

Windows Server 2000 has a limit of 2 TB.

You could have a 3Ware card that supports 12 SATA drives, and only would be able to create an array of 2 TB.

Thanks!

rjlee · 08-21-2004, 11:53 AM

Linux also has a 2 Terabyte limit, unless the LBD (large block device) option is compiled into the kernel. The LBD option sets the limit to 2 to the power 63 bytes (which is a very very big number, even compared to 2TB).

You can find out if you are using the LBD option with:

Code:

zcat /proc/config.gz | grep LBD

which should produce a line like this if the option is set:

Code:

CONFIG_LBD=y

If you want to enable the option, install the kernel source and open a root terminal. Change to /usr/src/linux and run

Code:

make cloneconfig xconfig

, and go to “device drivers”, then “block devices”, then select “Support for Large Block Devices”, and press ‘Y’. After that, save your changes (click the toolbar button), close the program with file/exit and run

Code:

make modules modules_install install && reboot

.

Alternatively, do this but press ‘N’ instead of ‘Y’ to turn the option off and gain a slight speed increase (on a 32-bit system).

jtl60047 · 08-21-2004, 09:06 PM

Thanks rjlee -

Glad I asked.