Hello all,
I am looking at using a hardware RAID device that appears to it's SCSI host as
a single large drive. I am well aware that I can break this device down into
multiple LUNS, but if possible I need to keep it as one big drive. I
understand from the Linux Info Sheet, last updated in 1998 according to it's
text, that Linux is able to handle partitions up to 4TB in size.
What I want to know is:
(a) Is 4TB still the maximum limitation on a single partition size? If not,
what is the current maximum?
(b) Would this maximum partition size still apply when using the software RAID
tools to combine two or more of these devices together?
What I am looking for is the ability to mount and format an external SCSI
device that's 3.5TB in size. (It's a Promise UltraTrak RM1500 w/ 15 x 250GB
drives). I want to be able to upgrade the hard drives at a later date and
know that the Linux box to which it is attached will still be able to handle
them. Ideally, I would like to purchase a second (or even a third) device
later down the road and use software RAID to concatenate them together.
Thanks for any help you can give,
Michael
On Tue, May 20, 2003 at 12:15:39PM -0400, Michael S. Peek wrote:
> I am looking at using a hardware RAID device that appears to it's SCSI host as
> a single large drive. I am well aware that I can break this device down into
> multiple LUNS, but if possible I need to keep it as one big drive. I
> understand from the Linux Info Sheet, last updated in 1998 according to it's
> text, that Linux is able to handle partitions up to 4TB in size.
What is the Linux Info Sheet?
AFAIK linux has never had a partition-limit of 4 TB.
There is a limit in any block-device of 2^32 sectors, typically 2 TB.
Some drivers may have sign-issues, leaving you with only 2^31 sectors (1
TB).
> What I want to know is:
>
> (a) Is 4TB still the maximum limitation on a single partition size? If not,
> what is the current maximum?
>
> (b) Would this maximum partition size still apply when using the software RAID
> tools to combine two or more of these devices together?
I believe the 2.4 kernel is still limited to 2 TB for both scsi-devices
and virtual block-devices such as md or lvm.
I think 2.5 has an option added for large block devices. This should
allow you to use both scsi-devices and md virtual devices larger than
2TB. It may depend on changes in the actual scsi-drivers, so possible it
only works for a subset of scsi-adapters. Last time I checked it didn't
enable larger LVM-volumes, so you're limited to md for virtual devices.
> What I am looking for is the ability to mount and format an external SCSI
> device that's 3.5TB in size. (It's a Promise UltraTrak RM1500 w/ 15 x 250GB
> drives). I want to be able to upgrade the hard drives at a later date and
> know that the Linux box to which it is attached will still be able to handle
> them. Ideally, I would like to purchase a second (or even a third) device
> later down the road and use software RAID to concatenate them together.
I think you would want to use LVM to concatenate them together, and
AFAIK that is not yet possible. There is work in progress though.
I think your best chances of making this work in the future without
having to reformat your system is to use LVM2 with a large physical
extentsize from the start.
My information may be out of date, so take this with a grain of salt.
--
Ragnar Kj?rstad
Zet.no