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Date:      Mon, 7 Mar 2005 18:06:52 +0300 (MSK)
From:      Dmitry Morozovsky <marck@rinet.ru>
To:        delphij@delphij.net
Cc:        freebsd-stable@freebsd.org
Subject:   Re: RELENG_5, snapshots and disk lock time
Message-ID:  <20050307180434.W4264@woozle.rinet.ru>
In-Reply-To: <20050307175506.H4264@woozle.rinet.ru>
References:  <20050307151733.I4264@woozle.rinet.ru> <1110205630.669.3.camel@spirit> <20050307175506.H4264@woozle.rinet.ru>

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Following up to myself

DM> XL> > dumping the snapshot of 140G ufs2 fyle system under contemporary RELENG_5 I 
DM> XL> > found that during mksnap_ffs file system is unresponsible even for reading for 
DM> XL> > more than 3 minutes (it's on modern SATA disk with 50+ MBps linear transfer). 
DM> XL> > Is it normal?
DM> XL> 
DM> XL> mksnap_ffs is expected to suspend your write access, but I think 3
DM> XL> minutes is too long for a 140G file system.  Would you please send the
DM> XL> dumpfs output of the said file system?
DM> 
DM> Well, as I said, it was even for read access. I checked this with the simple 
DM> shell script
DM> 
DM> #!/bin/sh
DM> 
DM> while true; do
DM> 	sleep 5
DM> 	date
DM> 	ls /lh/.snap
DM> done

It seems accessing snapshot directory is blocked for much more time than to 
other fs parts. Changing ls line to ``ls /lh'' leads to 

Mon Mar  7 18:02:58 MSK 2005
backup  home    local   pgsql   ports   src
Mon Mar  7 18:03:41 MSK 2005

so file system has been locked for approx 45 seconds. This seems more 
reasonable, but still seems a bit too long for me.


Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck@rinet.ru ***
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