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Message-ID: <52655C78.4080507@gmail.com> Date: Tue, 22 Oct 2013 00:55:20 +0800 From: Zheng Liu <gnehzuil.liu@...il.com> To: Andrei Banu <andrei.banu@...host.ro> CC: linux-ext4@...r.kernel.org Subject: Re: Weird jbd2 I/O load On 10/21/2013 10:24 PM, Andrei Banu wrote: > Hi Zheng, > > Thank you for your reply. We can make this test and if it doesn't help > we'll re-enable > the barrier but first I need to ask a few questions: > > 1. /dev/md2 is mounted on /. So your command should look like this? > > $ mount -t ext4 -o remount,barrier=0 /dev/md2 / Yes. > > In /etc/fstab I have other parameters as well: > noatime,usrjquota=quota.user,jqfmt=vfsv0 > Do I also add these like this: > > $ mount -t ext4 -o > remount,barrier=0,noatime,usrjquota=quota.user,jqfmt=vfsv0 /dev/md2 / If I remember correctly, this command is OK. But frankly I don't do the test. I am not sure all these options will pass when you remount a partition. > > 2. Can the command above be run on an active (very active) cPanel server? Sorry, I am not familiar with cPanel server. But if your previous testings run on a server under a heavy pressure. It quite impacts the result because disk bandwidth is occupied by this process. > > 3. How do I re-enable the barrier? sudo mount -t ext4 -o remount,barrier=1 ${DEV} ${MNT} > > 4. What is the probability of data loss in case of cold reboot? After disabling barrier, the system couldn't ensure that the dirty data has been written into the disk medium if your device couldn't support FUA command. So I just want to make sure that your SSD can not handle barrier command properly. *Please do not use 'barrier=0' in your product system*. - Zheng > > Thanks! > > On 10/21/2013 4:53 PM, Zheng Liu wrote: >> Hi Andrei, >> >> Could you please disable barrier for ext4 and try your 'dd' test again? >> $ sudo mount -t ext4 -o remount,barrier=0 ${DEV} ${MNT} >> >> *WARNING: you could lost your data with barrier=0 when you get a power >> failure or cold reset.* >> >> We have met a similar problem that is because some SSDs couldn't handle >> barrier command properly. >> >> Regards, >> - Zheng > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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