Solaris 10 : Disk features (part 1)
Monday Nov 20, 2006
Solaris 10 : Disk features (part 1)
Last week, I've already introduced ZFS and some basic features including some screenshots from my lab to help clarify the topics. Today, I'd like to talk a little bit about Solaris 10 in another aspect -- disk features -- how Solaris 10 manage physical disks, disk devices, device files, for examples.
The Solaris 9 prior to 4/03 only supports disk slice (aka partition) less than 1 TB. Why ? it is because the limitation of "Disk Label Header" which can not accommodate number of blocks more than 1 TB. This kind of overflow number is also affect the on-disk VTOC (Volume Table Of Content), device drivers and disk utilities (format, fmthard and prtvtoc).
In Solaris 9 4/03 or later and Solaris 10, the previous limitations have been modified to support bigger disk capacity (> 1TB) such as for ZFS the capacity is virtually unlimited.
For Multi-Terabyte disk capacity support, Sun has introduced the brand new Disk Label Header called EFI (Extensible Firmware Interface), device drivers and disk utilities that can easily manage not only multi-TB disk capacity but also bigger capacity in the future.
How about backward compatibility ?
To preserve the Disk Label Header compatibility :
- A disk or Logical Unit Number (LUN) smaller than 1 TB is accessed using the current VTOC structure.
- You access a disk or LUN exceeding 1 Tbyte using the new VTOC format.
- A disk or LUN smaller than 1 Tbyte that contains an EFI label is accessed by that label.
DIFFERENCES (EFI versus VTOC)
Supported by 64-bit Solaris[TM] 9 Operating System (04/03) and above only.
Provides support for disks greater than 1 terabyte in size.
Provides 7 useable slices - 0 thru 6 - where slice 2 is just another slice.
Solaris[TM] ZFS (Zettabyte File System) uses EFI labels by default.
Partitions (or slices) cannot overlap with the primary or backup label, or with any other partitions. The size of the EFI label is usually 34 sectors, so partitions start at sector 34. This feature means no partition can start at sector zero (0).
No cylinder or head information is stored in the label. Sizes are reported in sectors and blocks.
Information that was stored in the alternate cylinders area, the last two cylinders of the disk, is now stored in slice 8.
If you use the "format" utility to change partition sizes, the unassigned partition tag is assigned to partitions with sizes equal to zero. By default, the "format" utility assigns the "usr" partition tag to any partition with a size greater than zero. You can use the "partition change" menu to reassign partition tags after the partitions are changed. However, you cannot change a partition with a non-zero size to the "unassigned" partition tag.
EFI labels CAN be written to disks smaller than 1TB, where a standard VTOC label would normally apply, but VTOC cannot be forced onto devices larger than 1TB with. This can be done by running "format -e". When you attempt to "label" the disk, you will be asked which type of label is to be written.
Next topic, I will talk about how to determine what kind of on-disk VTOC being used on your disk or LUN. 8-0
Posted by DIrk on March 20, 2007 at 01:58 AM ICT #