[PLUG] Big Hard Drives (>137GB) on Linux
Keith Lofstrom
keithl at kl-ic.com
Fri Nov 7 10:58:12 UTC 2003
I use a number of large hard drives under Linux, with the 2.4.20 and
later kernels. Here's the scoop:
The new LBA48 drives can sometimes be jumpered down to an 8GB drive
(uh, who cares?) but other than that you need an LBA48 driver card.
The good news is that Alan Cox has written drivers for these, and
these drivers are in the recent kernels (and in Fedora, Redhat 10,
and probably the most recent Suse distros). The first drive will
probably show up in your system as /dev/hde . The second drive on
that cable would be /dev/hdf, on the second connector on the card
/dev/hdg, etc.
Most of the boards that come with the drives are rebranded Promise
boards. I have also seen HPT chipsets. A.C. built drivers for both.
Them's the good news. However, it gets weird if you get exotic.
With one of my motherboards, *two* drives on these cards gets confused;
the motherboard doesn't quite figure out which drive to boot from. On
another motherboard, boot works fine. That is with any combination of
one or more large and zero or more "small" drives. (120G is "small" :-) )
USB2:
You can also talk to these large drives with some of the USB2 interfaces.
I do this because I use the big drives for backup and want to hot swap
them. A.C. has written IDE hotswap drivers that work with the regular
cards, but these have not found their way into the mainstream kernels
yet. Probably by spring 2004. So, more about USB2:
You take a speed hit. The big drives are ATA-133 - that is a theoretical
raw 133MB/second, while the USB2 is theoretical raw 40MB/second. I have
never seen either interface reaching those speeds.
I have a SanDisk InClose removable drive swap rack, driven off USB2 -
this will talk LBA48. However, the card appears to suffer from buffer
overrun or something, and when I move large quantities of data very fast
(like 1GB/minute for 5 minutes) it sometimes locks up.
Today I will be trying out some ViPower IDE to USB2 swap racks; I want
to see if they suffer from the same overrun problem. They have a different
chipset. According to ViPower tech support, their cages work with the
large drives.
On external USB2 to IDE enclosures, the ADS LI5-USBX-804 enclosure will
not talk to LBA48 drives. The GWC Technology UD-200 USB to IDE adapter
cable will not talk to larger drives, but by Q1 2004 the UD-200A will
(according to email from their tech support).
There are a lot of other options out there. I hope I have conveyed the
impression that most things work with large drives most of the time, but
expect a little hassle, mostly hardware problems and not Linux problems
per se.
Most of the LBA48 solutions are described as "up to 300GB", while LBA48
has a theoretical maximum of 144,115,188 GB; however, I suspect that
by the time we get to those capacities we will be talking to the hard
drives very differently! At full ATA133, such a drive would take more
than 30 years to write. The 300GB limit is probably because the interface
makers don't have any larger drives to test with.
And yes, the new big drives ARE cool. But consider how you are going to
back them up!
Keith
--
Keith Lofstrom keithl at ieee.org Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs
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