On Mon, Jun 28, 2010 at 09:45:35AM +0100, Wayne Stallwood wrote:
On 28/06/10 00:26, (Ted Harding) wrote:
Just a guess -- and not inspired by any of the above -- is it by any chance trying to NFSmount a filesystem from a different host, not getting a response, and waiting till it times out?
I'd certainly hope not, given the delay is happening before the network is up :)
Chris, Why not temporarily disable ureadahead and see if that is the cause ?
I might try that, yes, thanks.
That said any delay that ureadahead is generating at that point *should* be saved later on in the boot process. The whole point being that it reads everything required for a boot in one pass and caches it in memory because this should be quicker than pulling in files one by one as needed. So while this delay might vanish when you turn off ureadahead you might find that the boot takes just as long..if not longer as everything else will be loading more slowly.
Although 15 seconds seems like a long time, is / on a slowish disk ? It is normal for ureadahead to take a bit longer after there has been a major system update as there will likely be lots of files it needs to reprofile, but after that it should be making an improvement.
My feeling too was that 15 seconds is a *long* time to be reading what is actually a fast[ish] SATA disk.
Another potential cause would be if something big was getting loaded at boot and it was taking ureadahead a while to get this off your disk and into memory, but for that sort of delay it would have to be pretty big. There is a guide somewhere on the ubuntu forums written by the ureadahead author to help with this sort of issue.
Hmm, I'm just running a test (a fairly naive test) of my disks' speed by copying 5Gb (8 CD images) from on drive to the other. It's taking a *long* time, just finished - 3 minutes and 4 seconds with 17 seconds of 'sys' time. That's around 40 seconds per Gb, 25Mb per second, not scintillatingly fast. I'm unfamiliar with modern disk speeds so I'm not at all sure if that's a reasonable speed or not.
A quick Google suggests that a 25Mb second transfer rate, reading one drive and writing to another, isn't too bad at all.