October 2014 - luv-main

Computer issues with Linux
by Brian May 19 Nov '14

19 Nov '14

Hello, Am having two strange problems that are starting to eerk me with this (relatively new) computer, running Debian wheezy: 1. If I boot anything later then 3.12 kernel, I don't get any display. As in the monitors display black. No cursors of any sort. Changing to a virtual console doesn't help. Booting in rescue mode doesn't help (I think this rules out X-Windows being a problem). If I go back to the 3.12 kernel, everything works perfectly. I also tried plugging monitors into alternative ports just in case it is going to the wrong place, but get nothing - in any case, under 3.12 the computer seems pretty good at automatically working out what ports are active under X-Windows. 01:00.0 VGA compatible controller: NVIDIA Corporation G96 [GeForce 9500 GT] (rev a1) Am currently using the non-free nvidia drivers. Had exactly the same symptoms when I installed the latest kernel without the non-free nvidia kernel modules. I think the problem is occurring before X starts. Computer seems to be up and running, and responsive to crl+alt+del despite not having a display. 2. There seems to be some weird performance problem. e.g. save a 2 kilobyte file in vim, and the computer can completely freeze (all other windows, including xterms, stop responding to user input) for, say 30 seconds, while it is writing that file. Chromium takes ages to load with several tabs, and pages can fail to start properly while it is doing so. Computer has 16GB RAM and is not using any swap. It has 11GB of buffer/cache space: total used free shared buffers cached Mem: 15G 13G 2.1G 0B 1.1G 7.9G -/+ buffers/cache: 4.6G 11G Swap: 3.8G 0B 3.8G Problems occurred before starting chromium, previously I wondered if it was chromium's fault. This is moving disk + RAID1 + LVM + ext4. Bonnie++ results seem to be pretty good, better in fact then my work computer, which doesn't suffer from similar problems. Writing a byte at a time...done Writing intelligently...done Rewriting...done Reading a byte at a time...done Reading intelligently...done start 'em...done...done...done...done...done... Create files in sequential order...done. Stat files in sequential order...done. Delete files in sequential order...done. Create files in random order...done. Stat files in random order...done. Delete files in random order...done. Version 1.96 ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP falidae 31904M 1228 94 107313 4 47471 2 +++++ +++ 137886 3 441.8 2 Latency 19141us 12435ms 251ms 19913us 88073us 283ms Version 1.96 ------Sequential Create------ --------Random Create-------- falidae -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ Latency 36us 223us 226us 36us 10us 24us 1.96,1.96,falidae,1,1404290654,31904M,,1228,94,107313,4,47471,2,+++++,+++,137886,3,441.8,2,16,,,,,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,19141us,12435ms,251ms,19913us,88073us,283ms,36us,223us,226us,36us,10us,24us I am currently working on a new theory that the performance problems only occur when the computer is cold and first turned on. I think I have seen evidence to disprove this, but guess I should run bonnie++ as soon as I turn the computer on, just to be sure. Any other ideas? Thanks -- Brian May <brian(a)microcomaustralia.com.au>

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Oracle and Linux
by Russell Coker 11 Nov '14

11 Nov '14

I'm writing this message as a Linux user and a member of LUV - not as a member of the LUV committee. Avi, you have a history of making good technical contributions to LUV and of representing your employer well. However I think that Oracle has been under- represented given their technical work and their importance in the industry. I think that it would be good to have some Oracle employees give talks at LUV meetings as they are doing a lot that LUV members could learn about. Avi you are obviously well qualified to give such talks, but I think it would be good to get other Oracle employees with different skills involved too. A lecture about running the Oracle Database on Linux would be of interest. Also Red Hat has been running free public events teaching people about their products and services which I have found to be good value (and I have recommended some on this list). Does Oracle run such events? If so please inform the LUV committee and we can forward to the list if appropriate (I don't think it's appropriate for Linux companies to advertise on this list, but it's OK for LUV members who aren't associated with companies in question to recommend them). Some years ago there was an Oracle database install-fest, that was a useful event and many people learned a lot there. I think it would be good if Oracle ran another of those, if that happens I think it would be appropriate for LUV to promote that. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/

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Free Ksplice for Ubuntu/Fedora
by Avi Miller 31 Oct '14

31 Oct '14

Hey guys, I'm not sure if you're all aware, but we make Ksplice updates freely available for Ubuntu[1] and Fedora[2]. Ksplice patches are provided for the LTS versions of Ubuntu and the latest two stable releases of Fedora (19 and 20 at the moment). If you've wanted to play with Ksplice technology and are not an Oracle Linux Premier Support customer, you can do it for free with either of these two products. If you want to see Ksplice in action on a RHEL box, you can get a 30-day trial[3]. If you're unaware of what Ksplice is, it's rebootless kernel patching of security and bug fixes. Ksplice is in the same space as Kpatch and kGraft, but is a far more mature technology and is able to currently patch far more of the kernel in runtime than its competitors. For more information, see https://www.ksplice.com/paper Cheers, Avi [1] https://www.ksplice.com/uptrack/download-ubuntu [2] https://www.ksplice.com/uptrack/download-fedora [3] https://www.ksplice.com/rhel-signup

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Btrfs news: 3.17.2 (and others) released
by Chris Samuel 31 Oct '14

31 Oct '14

Looks like Greg KH has released these 4 kernels, each with btrfs patches: drwxrwxr-x 2 chris chris 4096 Oct 31 19:09 3.10.59 drwxrwxr-x 2 chris chris 12288 Oct 31 19:09 3.14.23 drwxrwxr-x 2 chris chris 16384 Oct 31 19:09 3.16.7 drwxrwxr-x 2 chris chris 20480 Oct 31 19:09 3.17.2 If you're using one of those series with btrfs you'll be wanting to upgrade.. -- Chris Samuel : http://www.csamuel.org/ : Melbourne, VIC

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Re: OpenSuse with Btrfs (and limitations), Chris Mason describes Btrfs as "stable"
by Peter Ross 31 Oct '14

31 Oct '14

Hi, From: "Russell Coker" <russell(a)coker.com.au> > On Fri, 31 Oct 2014, "Peter Ross" <Petros.Listig(a)fdrive.com.au> wrote: >> The article also mentions some speed issues especially in relation to >> databases. > > COW filesystems use different blocks on disk every time a file is written > to. Yes. >> I would be interested to know what Oracle says to databases on ZFS on >> Solaris - and Btrfs on Linux systems (the later not supported by Oracle >> yet, I believe, the first I am not sure about) > > The same performance issues apply to BTRFS and ZFS. The significant > difference is that L2ARC and ZIL can mitigate such problems So Btrfs does not have this kind of features, I understand. Thanks for pointing this out. >> My gut feeling: Use Btrfs for "bread and butter" work and not if you need >> 101% reliability. With backups and mirrors and failovers (which may be >> in place anyway) you may be fine. > > If you want good reliability then you need backups and mirrors anyway. Yes, no doubt. But failover is a bit more tricky if you are dealing with instable nodes. It is harder to catch an error (which triggers a failover) if there are many ways to fail and some quite unexpected. For the purpose of explanation: A switched off computer is easier to detect than some data inconsistency which may "sleep" for a while before being detected. You are buggered if you have two nodes with different issues then. >> I just do not get my head around why a subvolumes is called subvolume if >> it is (according to the FAQ) comparable to a file system - you just can >> have many of them in a pool. > > A subvolume is represented inside BTRFS in much the same way a directory. You > can't mount one subvol without operating on the rest of the filesystem, so if > a filesystem is corrupted such that it can only be mounted RO then that > applies to all subvols. My tube may be glued to a wheel so you may have to replace the wheel in order to replace the tube. But I doubt that it makes my tube a wheel;-) Something that is represented in much the same ways as a directory does not look like a volume to me. Every "subvolume" has a root, it can be mounted everywhere on the system - as a file system does. It is organized on top of a block structure which abstracts from physical devices (usually referred to as logical volumes) and creates a directory structure on it - as a filesystem does. My way of thinking of things and analogies and my imagination feels slightly tricked by btrfs terminology;-) But I won't continue arguing. I have been walking through the mountains in a fog and I looked at a map and tried to make sense, until my friend rotated the map by 180 degrees and we realized how much we lost orientation... I guess you walked through the Btrfs forest a bit longer than me. Talking of forests - that's how I would call the whole "bunch of filesystems" directory structure on top of a pool because you can have many trees (filesystems) with their own roots in it (while a traditional block device has one only) Cheers Peter

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Re: OpenSuse with Btrfs (and limitations), Chris Mason describes Btrfs as "stable"
by Peter Ross 31 Oct '14

31 Oct '14

From: "Avi Miller" <avi.miller(a)gmail.com> >> On 30 Oct 2014, at 6:33 pm, Andrew McGlashan >> <andrew.mcglashan(a)affinityvision.com.au> wrote: >> >> Hi Avi, >> >> On 30/10/2014 12:33 PM, Avi Miller wrote: >>> FYI, while it's not the default filesystem, you can do the same on >>> Oracle Linux 6 and 7 when using btrfs as the root filesystem and >>> installing yum-plugin-fs-snapshot. btrfs is available in the default >>> Oracle Linux 7 installer as a filesystem option and if you want to >>> install OL6 with a btrfs root, use the UEK-based boot ISO and a network >>> install source. >> >> I believe the point was that it was "stable" subject to some serious >> omissions for things you would like to do .... particularly with >> "receive" being "totally disallowed" ... > > Yeah, not sure why SUSE chose to disallow those features. Most of those > (with the exception of the truly in-development stuff like RAID5/6) are > allowed and supported on Oracle Linux. We believe btrfs to be stable even > with those features active. The article also mentions some speed issues especially in relation to databases. I would be interested to know what Oracle says to databases on ZFS on Solaris - and Btrfs on Linux systems (the later not supported by Oracle yet, I believe, the first I am not sure about) I am using ZFS, and compare Btrfs to it (e.g. to use similar technologies on Linux machines). At the moment I stick with FreeBSD where I can (and can choose) because overall it makes some work easier for me while doing the same job in many cases. BTW: Oracle VM (A Xen based virtualization host) surprised me recently. The standard installation configured plain ext(ext3, I think but not sure) filesystems on a standalone server and later warned me about using it as the storage space for the VM disks (unfortunately I forgot exactly what it was, it was about "missing features" on it - and it was not the obvious about local storage which is not shared). (I have replaced it by something more bizarre so I cannot confirm details anymore, sorry) Sometimes I just write to share information;-) It was not meant to be a particular endorsement or the opposite. My gut feeling: Use Btrfs for "bread and butter" work and not if you need 101% reliability. With backups and mirrors and failovers (which may be in place anyway) you may be fine. It would work in my work environment, I reckon. I just do not get my head around why a subvolumes is called subvolume if it is (according to the FAQ) comparable to a file system - you just can have many of them in a pool. So please call it a "filesystem". It is not a volume at all. The pool is! But that may be too late to change. It is just a bit like calling a tube a wheel - but only on my bicycle. My wheel got a puncture. Can you replace it? So for "my bicycle" you have to relearn terminology - or I get a new wheel instead a new tube because you "misunderstood". Regards Peter

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Re: OpenSuse with Btrfs (and limitations), Chris Mason describes Btrfs as "stable"
by Peter Ross 31 Oct '14

31 Oct '14

From: "Avi Miller" <avi.miller(a)gmail.com> Hi, > >> On 31 Oct 2014, at 9:58 am, Peter Ross <Petros.Listig(a)fdrive.com.au> >> wrote: >> >> The article also mentions some speed issues especially in relation to >> databases. > >> The standard installation configured plain ext(ext3, I think but not >> sure) >> filesystems on a standalone server and later warned me about using it as >> the storage space for the VM disks (unfortunately I forgot exactly what >> it >> was, it was about "missing features" on it - and it was not the obvious >> about local storage which is not shared). > > Local storage on Oracle VM is ext3 because it only stores the Dom0 > software. The actual VM disk storage is either on OCFS2 (on FC/iSCSI > shared storage) or NFS. We require OCFS2 for its clustering capabilities. > You can use extra local storage as VM disk storage on Oracle VM 3.3 now > too, which is also formatted OCFS2. I expected this. I did not give the install a SAN disk and it took all available diskspace to format with ext3. Maybe I just forgot to click/unclick something during installation, not sure. I made a "dumb install" and thought: Let it take care of the details, don't change defaults. > Because it's a subvolume. :) It's not a filesystem, because subvolumes > appear in their parent volumes, but can also be mounted independently. <nit-picking> I never mount volumes, I mount filesystems. According to "Unix philosophy", it does not matter where filesystems are, you can mount them everywhere in a filesystem tree which has one root. And the btrfs default is mounting in the parent .. filesystem which is on the same pool. </nit-picking> Regards Peter

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OpenSuse with Btrfs (and limitations), Chris Mason describes Btrfs as "stable"
by Peter Ross 30 Oct '14

30 Oct '14

In an e-mail to Heise Open (a bit like "German slashdot"), Chris Mason describes Btrfs as "stable" http://www.heise.de/open/meldung/Btrfs-Erfinder-stuft-sein-Linux-Dateisyste… (the original e-mail embedded as a picture) According to his e-mail he and others are focusing on RAID5/6 which is not production ready yet. Suse makes Btrfs the default OS filesystem for SLE 12. It uses snapshots when updating the system so you can rollback anytime (As Solaris and PC-BSD do with ZFS, btw. The PC-BSD Grub boat loader is modified to allow to choose ZFS snapshots - I wonder whether the SLE Grub allows the same in Grub as well) Compressions seems to be considered as "not ready yet" either, it is disabled via kernel module defaults. More here: http://kernel.opensuse.org/cgit/kernel-source/tree/patches.suse/btrfs-8888-… Disallow access to filesystem with unsupported features by default but leave a chance to access the filesystem via module parameter override (taints kernel). The status can be toggled during runtime by changing the exported module parameter in /sys/module/btrfs/parameters/allow_unsupported. Current: - mount: inode_cache - deny mount - mount: autodefrag - deny mount - ioctl: fallocate and hole punch - return, warning printed only once - ioctl: receive - completely disallow - ioctl: device replace - disallow - mount: raid56 - remount RO - mount: compression - deny mount - mount: seeding device - deny mount - balance: use of raid56 taints kernel - chattr: +c - disallow, no change Having "receive" disabled removes half of the fun.. Regards Peter

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RT
by Russell Coker 29 Oct '14

29 Oct '14

I have a RT 3.6 installation that I don't know how to operate. The person who was doing the support work left suddenly and I've got to provide access for their replacement. I have an account in RT that I used for test purposes some years ago but I don't remember much about it. How do I create a new account and lock the account of the old support person? If someone has good RT sysadmin skills and wants to tender for the work of configuring this (and maybe upgrading RT to the latest version) then contact me off list. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/

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Speakers for November and future meetings
by Andrew Pam 28 Oct '14

28 Oct '14

We are just finalising the programme for the November meeting next week, and if any members have a topic they would like to speak about either on Wednesday 5 November or at a later meeting, or know someone who they would like to hear speak, or would like to suggest a topic they would be interested in hearing about, please do contact the LUV committee and let us know! Thanks, Andrew

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