hot plugable?

hot plugable?

[Andreas Jellinghaus]

Hi is there any ata or sata driver that allows hotplugging with linux?

combined with software raid, could it be configured, so I can replace a
disk and repair the raid without any reboot necessary?

or will this only work with hardware raid controllers? I'm looking for 
a software raid solution, because raidtools and smartmon are both very
nice, while many tools for hardware raid controllers are not that nice
to use.

If there is such a chipset/driver, are there any benefits a hardware raid
controller has over such a software raid solution? Sure, hardware raid
controllers do the raif5 calculations for you, and the data only passes
system bus once in normal operation / not at alle for restoring data.
But with modern cpu and busses these issues might not be very important
any longer?

Thanks for your advice.

Regards, Andreas

Re: hot plugable?

[J. Ryan Earl]

Andreas Jellinghaus wrote:

>Hi is there any ata or sata driver that allows hotplugging with linux?
>
>combined with software raid, could it be configured, so I can replace a
>disk and repair the raid without any reboot necessary?
>  
>
I don't think libata supports it yet, so you're SOL with most serialATA 
controllers.

Only certain hardware supports it (ie 3ware), but sometimes hardware 
performance can be surprising low compared to software RAID solutions.  
You'd have to test to see which solution worked best for you.

-ryan

Re: hot plugable?

[Ryan]

> All SATA HWIF chips support hot-swap (AFAIK), however, none are 
> supported under Linux because libata does not support it.  I think this 
> is what I said originally.  For some reason, libata supports everything 
> to do with power management, and nothing to do with hot-plugging.  =(

True, that.  Hotswap is part of the SATA standard, after all.  I just hope it
won't stay that way forever...

> It seems that particular hardware has premature support under Linux.  I 
> would be worried about disk compatibility with other 
> controllers/interfaces too, though I'm sure there are methods to 
> transfer your volumes over to a new controller, it would prolong and 
> complicate in place upgrades for people doing things on the cheap.

I'm not worried about this as it's not a production-level server and downtime is
of no consequence.  I'm willing to move my data to another location in order to
recreate the array if/when the necesary support becomes available.  Of course,
not having 240gb on any one machine other than the server really does
cmoplicate things...but I know people  >8)
 
> It may take some time for the SX4 to have mature support under Linux.  
> 3Ware is the only open-driver hardware that has a driver capable of 
> hotplug that I know of, but it gives dubious performance.  I pray for 
> the day libata does hot-swap so that I don't have to standardize on any 
> slow hardware platforms for hot-swap.    I'm excited about getting the 
> twin Raptors off the PCI bus/siimage and directly onto the 
> southbridge/sata_via.

I hope to see some progress toward that end.  Supposedly Promise is offering
support to kernel developers, but since I'm not involved with any kernel
development, much less libata, I don't know for sure.  We can only take the
developers' word for it and hope  >8)

> 
> -ryan
> 

-ryan

-- 
huh?

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