Informix

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  • 1.  Finding new BBS difficult

    IBM Champion
    Posted Tue March 31, 2020 11:50 PM
    Folks,

    First, let me admit that my (alleged) mind isn't what it once was.

    I haven't really used the new forum much.  I find it somewhat confusing and difficult to use.

    The only IBM product in which I am interested is Informix, and the new formum doesn't seem to provide the same functionality that the old one did.  For example, today, I am finally trying to use the new forum, and, finally (after having to login twice), I think I get to the Informix forum.  I look for a search mechanism, but, the only thing I see is the little search box at the upper right hand part of the page.  There doesn't appear to be any way to control the search.  It would seem that all you can do is enter one or more terms.

    So, I enter ZFS (our Oracle VAR [we have Oracle, nee SUN, servers) is trying to get us to buy new hardware, and to use ZFS for Informix because, "You can easily back up your database with Solaris 11 by merely quiescing it and taking a snapshot."  When I responded that I preferred to use an Informix utility because then I can do a backup while maintaining the database 100% online, the tech rep responded that he wasn't familiar with Informix and that the way he recommended was the way he did it with Oracle.  (Too bad for the "O" folks, I guess.)  I also told him we didn't use the file system for our database storage because we use raw devices, and I wondered how that could work with ZFS.  He replied there was no problem.  So, that made me curious, and I figured I'd check in the IIUG forum to see what I might glean about Informix and ZFS.

    Anyway, I think I am in the Informix discussion group, and I enter "ZFS" as a search term.  I get two hits, neither of which has anything to do with Informix.  (The search returned DB2 material.)

    Is there any way to search only in the Informix group with this new forum?  Is there any way to control the time span over which the search occurs?  Or whether the search terms are "AND" or "OR"?

    In the mean time, I can use the old forum as a resource, but, as time passes, it will become less and less current.

    Thank you.

    DG

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    David Grove
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    #Informix


  • 2.  RE: Finding new BBS difficult

    Posted Wed April 01, 2020 04:01 AM
    Hi David,
    Since the first article on this forum is less than a year old, I think it's rare that the search results will be helpful when compared to the previous iiug forum.
    For discussions about using zfs, please read the previous forum article and Art's blog post, or I'm sure you'll get a great answer if you wait soon.

    http://informix-myview.blogspot.com/2010/07/new-journaled-filesystem-rant.html
    http://members.iiug.org/forums/ids/index.cgi/noframes/read/26228

    ------------------------------
    SangGyu Jeong
    Software Engineer
    Infrasoft
    Seoul Korea, Republic of
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  • 3.  RE: Finding new BBS difficult

    IBM Champion
    Posted Wed April 01, 2020 09:10 AM
    David:

    On the new forum itself, note that the old forum and comp.databases.informix Usenet group history are not yet available. I am working, as IIUG Board liaison to the group at IBM that owns these forums, to get the history added to the system, but it is taking time and the Corvid-19 situation isn't helping. We will get it done, but until then ... 

    I will bring up your thoughts about expanding the capabilities of the search feature though so that one can limit searches to one forum or a group of forums. This is a good idea.

    On ZFS, it isn't a bad filesystem for performance over all because it only journals metadata not data blocks. However, instead of journalling data blocks ZFS uses a copy-on-write scheme to improve data safety and slightly improve write performance. The downside of that schema is that whenever Informix writes to a data page the whole block that contains that 2K, 4K, etc. page, which may be as large as a GB, gets written somewhere else on the disk which means that pages that Informix thinks are contiguous are not. Now with SSD and other solid state drives now common, that is less of an issue than it was before, remember that SSD drives internally are doing the same kind of copy-on-write in order to prevent individual data cells from prematurely reaching their write limit before the drive as a whole does. That means that ZFS may cause even more cells to age even faster than a "normal" file system. So, I am not a fan.

    As far as using ZFS snapshots for backups, like you I prefer to use old reliable ontape or onbar which do not require that I issue an 'onmode -b block' which can be disruptive no matter how fast the snapshot is. I would recommend that you continue to use ontape or onbar writing to a ZFS filesystem which is then snapshotted or otherwise backed up to separate media.

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    Art Kagel
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  • 4.  RE: Finding new BBS difficult

    IBM Champion
    Posted Wed April 01, 2020 09:16 AM
    I used to have Cdi/forum indexed and searchable but I was told to take it down

    Cheers
    Paul

    Paul Watson
    Oninit LLC
    +1-913-387-7529
    www.oninit.com
    Oninit®️ is a registered trademark of Oninit LLC





  • 5.  RE: Finding new BBS difficult

    Posted Wed April 01, 2020 11:07 AM
    Informix works fine with ZFS, however couple of things, mostly related to performance, need to be taken into account.

    One of these is ZFS configuration. If we take a disk or a small number of regular disks and compare I/O performance for Informix using ZFS vs raw devices - the ZFS performance will likely be awful - for checkpoints, LRU writes, etc. For decent performance ZFS must have fairly complex configuration, including the intent log  ( "ZIL" ) and, possibly, additional cache ( "L2ARC" ) both on the devices capable of supporting high rate of random I/O operations. In addition, whole ZFS performance usually is limited by slowest virtual device  in the pool, so it's important to pay attention to how vdevs are created.

    Another thing,  which by the way was causing Oracle a lot of grief in most/all recent releases of the Solaris O/S, is the fact that ZFS not only gobbles huge amounts of memory, but, in addition, it's extremely hard for the applications and O/S to take this memory back. Considering the fact that Informix works best with large memory footprint, and the fact that there is no direct I/O support in ZFS - all dbspaces will try to find way to be cached in memory by ZFS. There are several parameters to limit ZFS memory consumption, the point however is - without special attention to this it's possible to get into situation where Informix could not even be restarted, because ZFS will use all available memory. One can observe memory used by ZFS by running this one-liner (as root) :

     echo "::memstat" | mdb -k

    After ZFS grabs enough memory it will be difficult for the applications, including Informix, first to allocate memory using larg(er) pages and, in extreme cases,  it may not be possible to (re)start.
     
    In Solaris 11.4 there is a feature called "memory reservation" or something similar - as one more attempt to address this issue. Systems that expect good performance both from the database server and ZFS - must have a lot of RAM so that each can be given sufficient amount of memory.

    Other that that - ZFS features like compression, encryption, deduplication, snapshots, ease of administration, etc. - make it  a really attractive choice, and if it's given proper resources and correctly configured - it also performs quite well.

    I will not comment on backup side of things, in most cases given snapshot'ed set of dbspaces Informix will be able to go through recovery and come up even if snapshot is taken without blocking checkpoint, but that't something, to my knowledge, that had not been extensively explored.

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    Vladimir Kolobrodov
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  • 6.  RE: Finding new BBS difficult

    IBM Champion
    Posted Wed April 01, 2020 12:52 PM
    Thank you all, for your fast and helpful replies.

    DG

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    David Grove
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