[OpenIndiana-discuss] ZFS pool slow as molasses

Andrew Gabriel illumos at cucumber.demon.co.uk
Tue Oct 5 21:06:11 UTC 2010

Julian Wiesener wrote:
> On 10/ 5/10 10:13 PM, Paul Johnston wrote:
>> Er what sort of name would you expect to see for a sata device?
> SATA devices normaly have a Taget, so it's c4t0d0 instead of c4d0. 
> However, these are names, if you want to know what interface type is 
> used, you should look on the device path:
> This is what an SATA device looks like with Native AHCI disabled:
> $ ls -la /dev/dsk/c7d0s0
> lrwxrwxrwx   1 root     root          51 May 23  2009 /dev/dsk/c7d0s0 -> 
> ../../devices/pci at 0,0/pci-ide at 1f,2/ide at 0/cmdk at 0,0:a
> This is what an SATA device looks like with Native AHCI enabled:
> $ ls -la /dev/dsk/c3t0d0s2
> lrwxrwxrwx   1 root     root          49 Jan  6  2009 /dev/dsk/c3t0d0s2 
> -> ../../devices/pci at 0,0/pci1028,283 at 1f,2/disk at 0,0:c
> Many especially older systems have it disabled by default because 
> Windows was not able to boot from SATA devices in the past. Also some 
> vendors disabled the Native AHCI switch in their BIOS. If you're lucky 
> an BIOS update will make it available, if not, you're out of luck (or go 
> to the fency BIOS hackers crowd and possible trash your BIOS).

If you upgraded from a build which didn't have a native sata driver for 
your chipset (and hence drove it as ATA), to a later build with a native 
sata driver, the old device name with a 't' is preserved but now points 
to the new sata driver, so any /dev/dsk/... entries in vfstab and the 
like didn't get screwed up. If you then add another sata disk to the 
system, that gets a new device name with a 't'.

Confused when I first saw this, but it makes sense.


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