system hangs during dump + compress > usb2-drive
jguojun at sbcglobal.net
Mon Oct 1 18:03:16 UTC 2012
From: Xin Li <delphij at delphij.net>
To: Jin Guojun <jguojun at sbcglobal.net>
Cc: questions at freebsd.org; hackers at freebsd.org
Sent: Sun, September 30, 2012 1:07:40 PM
Subject: Re: system hangs during dump + compress > usb2-drive
On 9/29/12 10:49 PM, Jin Guojun wrote:
> In FreeBSD 8.3 release (possibly in earlier release), dump a file
> system has 2-3GB or more content can cause system hang in a
> specific case (pipe to compression):
> dump FS-on-SATA-drive > usb-drive OK dump FS-on-SATA-drive
> | anyCompress > sata-drive OK mv a-large-dump-file from
> STAT drive to a USB drive OK dump small-FS-on-SATA-drive |
> anyCompress > usb-drive OK small -- 1.8GB or less dump
> large-FS-on-SATA-drive | anyCompress > usb-drive hang
> content is 3GB or larger (did not try around 2GB yet)
> When system hangs, no sub system, such video, network, etc, will
> function. Typically, the unfinished compressed dump file is around
> 1.5-2.7GB, so guessing dumped file content is close to or over 2GB
> when failure occurred.
> Has anyone encountered the same problem?
> Because this usually takes a few hours to occur, this is hard to
> watch how/when it happens. Is any way to debug or determine what
> status the system is?
For starters I'd use a different console for doing procstat -kk -a and
see what the system is doing. (Perhaps also top)
I *think* that if it's just hanging for some time, it's probably
because the system is trying to take a snapshot? It takes time on UFS
when creating and removing the snapshot. Just a guess...
Not sure how to use a different console. No tty is functioning (neither ttyv?
nor over network).
You are right on a different case --
mount /dev/da0s4d /mnt # mount a usb drive
ssh remote-liux-host "tar -cf - 8GB_FS" | tar -xf -
In this case, doing ls -l /mnt or df will hangs, but system is still alive. The
network is 45Mbps.
I have no idea how long it took the tar to finish since machine is 60 km away.
When I left there last Friday, only 400MB was done in one hour. I will get the
processing time tomorrow.
The problem we can see now is that tar (probably the pipe) process only finish
Filesystem 1K-blocks Used Avail Capacity Mounted on
/dev/ad4s3a 1012974 355348 576590 38% /
devfs 1 1 0 100% /dev
/dev/da0s4d 1027486774 4198246 941089588 0% /mnt
So, I suspect this is a pipe problem, not a compress issue.
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