Hello, Fascinating.. I can finally see some cause/effect. Your method worked: > # dd if=/dev/urandom of=/dev/sdc2 > # mkfs -t nilfs2 -v /dev/sdc2 <-- does the TRIM request > # dd if=/dev/sdc2 iflag=direct 2> /dev/null | hexdump What's interesting is in a working case, every 16mbyts of zero's there is ~4k non-zero/random data. I'm assuming this is the way it is supposed to work. Also, given this new test I determined that TRIM does NOT work on the flash part on our target system, so the original message is legitimate: "NILFS warning: error -95 on discard request, turning discards off for the device" Thank you both for your helpful input! Regards, Mark Trumpold > -----Original Message----- > From: Ryusuke Konishi [mailto:konishi.ryusuke@xxxxxxxxxxxxx] > Sent: Thursday, September 06, 2012 3:02 AM > To: Mark Trumpold > Cc: Vyacheslav Dubeyko; linux-nilfs@xxxxxxxxxxxxxxx; Eric Rodriguez > Subject: Re: 'nilfs' TRIM issue? > > On Wed, 5 Sep 2012 13:52:20 -0700, Mark Trumpold wrote: > > Hello Vyacheslav, > > > > > Do you use NILFS as root file system? > > > > > Actually, 'nilfs' on this system is just a container that contains > > loop images, one of which is the root filesystem. As you can see this > > is a little out of the norm, so I think I should do more homework > > before involving a lot of your time.. At this point it in not clear > > if TRIM is working at all for 'ext4' or 'nilfs' on our system. It may > > be that the warning from 'nilfs' is legitimate. > > Actually, ext4 does not emit warning even if the TRIM is not supported by > underlying block devices; it simply ignores the error status of the discard > request. > > > I think it might be best for me to first find a way to test whether or > > not TRIM is working in general for a particular configuration. > > I've gone to a totally generic system with just a test 'nilfs' and 'ext4' > > partition to get some experience. One thing I've noticed is 'ext4' > > does not complain if you mount with 'discard' on a device that does > > NOT support it -- so that's no help. > > > > I've tried the following simple sequence: > > dd if=/dev/urandom of=tempfile bs=1M count=3 > > hdparm --fibmap tempfile <-- get start address of the file > > hdparm --read-sector [ADDRESS] /dev/sda rm tempfile && sync && sleep > > 120 > > hdparm --read-sector [ADDRESS] /dev/sda <-- should be all zero's > > > > Got this off the Internet. The last step NEVER returns zero's for > > either 'nilfs' or 'ext4'. > > > > If you happen to know of a better test, that would be appreciated. > > mkfs.nilfs2 issues TRIM/DISCARD by default. > > With mkfs.nilfs2, you can test if the TRIM is supported on the device if you > have an empty partition: > > # dd if=/dev/urandom of=/dev/sdc2 > # mkfs -t nilfs2 -v /dev/sdc2 > > where /dev/sdc1 is the empty partition in this example. > > You will see the following message if TRIM is supported. > > Discard succeeded and will return 0s - skip wiping > > Then, you can confirm the device is actually cleared, for exapmle, with dd > command: > > # dd if=/dev/sdc2 iflag=direct 2> /dev/null | hexdump > > > With regards, > Ryusuke Konishi > > > > Thanks for your attention. > > Best regards, > > Mark Trumpold > > > > > > -----Original Message----- > > From: Vyacheslav Dubeyko [mailto:slava@xxxxxxxxxxx] > > Sent: Tuesday, September 04, 2012 11:31 PM > > To: Mark Trumpold > > Cc: 'linux-nilfs@xxxxxxxxxxxxxxx' > > Subject: Re: 'nilfs' TRIM issue? > > > > Hi Mark, > > > > On Tue, 2012-09-04 at 16:32 -0700, Mark Trumpold wrote: > > > Greetings, > > > > > > I am seeing the following message a few minutes after booting a system: > > > > > > > Do you use NILFS as root file system? > > > > > "NILFS warning: error -95 on discard request, turning discards off for the > device" > > > > > > > As I can see from message that operation is not supported (-95). So, it > means that you try to use discard in the case of no support of it on the flash. > > > > How did you mount NILFS (I mean mount options)? > > Could you share mount utility output without any options? > > Could you share content of your fstab file? > > > > > We are using the "Satadom-150" flash part which does support TRIM, > > > as evidenced by 'ext4' filesystems having no issue with the mount > 'discard' option. > > > > > > > You want that it hasn't any error message when you use 'discard' mount > option in the case no support of it on flash. Am I correct? > > > > With the best regards, > > Vyacheslav Dubeyko. > > > > > > > I am running: > > > Debian 6.0.5 > > > Linux kernel 3.3.1 > > > Nilfs-utils 2.1.1 > > > > > > Any thoughts would be greatly appreciated. > > > > > > Thanks in advance, > > > Mark Trumpold > > > > > > > > > Confidentiality Notice: The information contained in this electronic e-mail > and any accompanying attachment(s) is intended only for the use of the > intended recipient and is confidential and/or privileged. If you and we have a > confidentiality agreement or other non-disclosure obligations between us, > this Notice shall be deemed to mark and identify the content of this email > and any attachments as confidential and proprietary. If any reader of this > communication is not the intended recipient, unauthorized use, disclosure or > copying is strictly prohibited, and may be unlawful. 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