On 22.03.2010 18:10, Richard Elling wrote:
On Mar 22, 2010, at 7:30 AM, Svein Skogen wrote:
On 22.03.2010 13:54, Edward Ned Harvey wrote:
IIRC it's "zpool scrub", and last time I checked, the zpool command
exited (with status 0) as soon as it had started the scrub. Your
command
would start _ALL_ scrubs in paralell as a result.
You're right. I did that wrong. Sorry 'bout that.
So either way, if there's a zfs property for scrub, that still doesn't
prevent multiple scrubs from running simultaneously. So ... Presently
there's no way to avoid the simultaneous scrubs either way, right? You have
to home-cook scripts to detect which scrubs are running on which
filesystems, and serialize the scrubs. With, or without the property.
Don't get me wrong - I'm not discouraging the creation of the property. But
if you want to avoid simul-scrub, you'd first have to create a mechanism for
that, and then you could create the autoscrub.
Which is exactly why I wanted it "cooked in" in the zfs code itself. zfs
"knows" how many fs'es it's scrubbing.
Nit: ZFS does not scrub file systems. ZFS scrubs pools. In most deployments
I've done or seen there are very few pools, with many file systems.
For appliances like NexentaStor or Oracle's Sun OpenStorage platforms, the
default smallest unit of deployment is one disk. In other words, there is no
case where multiple scrubs compete for the resources of a single disk because
a single disk only participates in one pool. In general, resource management
works when you are resource constrained. Hence, it is quite acceptable to
implement concurrent scrubs.
Bottom line: systems engineering is still required for optimal system operation.
-- richard
When you hook up a monstrosity like 96 disks (the limit of those
supermicro 2.5"-drive sas enclosures discussed on this list recently) to
two 4-lane sas-controllers, the bottleneck is likely to be your
controller, your pci-express-bus, or your memory bandwidth. You still
want to be able to put some constraints into how much your pushing the
hardware. ;)
//Svein
--
Sending mail from a temporary set up workstation, as my primary W500 is
off for service. PGP not installed.
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