Limited number of 2 GB chunks on big disks
Hi Is it possible to use chunks bigger than 2 GB. There is a limited number of partitions (on UNIX) on big disks (36 GB). I can't use whole disk if I want to have chunks on raw devices. Is there only solution to have chunks on files, what about performance ?! thanks Miran
>Subject: Limited number of 2 GB chunks on big disks >From: Miran Nikolic miran.nikolic@telekom.si >Date: 07.06.00 09:33 W. Europe Daylight Time >Message-id: <393DFAD3.7F69AA18@telekom.si> > > Hi > >Is it possible to use chunks bigger than 2 GB. There is a limited number >of partitions (on UNIX) on big disks (36 GB). I can't use whole disk if >I want to have chunks on raw devices. Is there only solution to have >chunks on files, what about performance ?! > > thanks > Miran > > > > > > > > > yes. Install the Informix Enterprise Decision Support server. Nona
> >Is it possible to use chunks bigger than 2 GB. There is a limited number > >of partitions (on UNIX) on big disks (36 GB). I can't use whole disk if > >I want to have chunks on raw devices. Is there only solution to have > >chunks on files, what about performance ?! No, you cannot used chunks with more than 2 GB. What kind of OS do you use? What is your partition number limit? If you use cooked files, your problem number one is not performance. Your problem number one is the file system buffer of your OS. So it is possible, that Informix think it's buffer-cache is flushed to disk, but it still resides in the fs write buffer of OS. In case of a crash of your system, your data will be inconsistent and you have to restore your Informix instance. Wile
Watawinowa, Watawinona wrote: > >Is it possible to use chunks bigger than 2 GB. There is a limited number > >of partitions (on UNIX) on big disks (36 GB). I can't use whole disk if > >I want to have chunks on raw devices. Is there only solution to have > >chunks on files, what about performance ?! > yes. Install the Informix Enterprise Decision Support server. If you have a Cessna, whose luggage box would be to small, would you use a 747, instead? Wile
"Wile E. Coyote" wrote: > > > >Is it possible to use chunks bigger than 2 GB. There is a limited number > > >of partitions (on UNIX) on big disks (36 GB). I can't use whole disk if > > >I want to have chunks on raw devices. Is there only solution to have > > >chunks on files, what about performance ?! > > No, you cannot used chunks with more than 2 GB. What kind of OS do you > use? What is your partition number limit? > > If you use cooked files, your problem number one is not performance. > Your problem number one is the file system buffer of your OS. > > So it is possible, that Informix think it's buffer-cache is flushed to > disk, but it still resides in the fs write buffer of OS. In case of a > crash of your system, > your data will be inconsistent and you have to restore your Informix > instance. This is a common misconception. Informix Dynamic Server (though not SE) opens ALL chunks that are NOT RAW in O_SYNC mode so that the write system call will not return until the system buffers used by that I/O have been flushed to disk. If you use IDS your data is ALWAYS SAFE. This is not the problem. PERFORMANCE IS! The extra copy to from the Informix buffers to the OS buffer cache is expensive and will slow you down 10-20% if you use a COOKED (ie block) device, such as /dev/dsk/c0t3d1s4, as opposed to the identical RAW (ie character) device, which would be /dev/rdsk/c0t3d1s4. If you use a filesystem file you incurr an additional performance penalty of from 5-15% depending on how fragmented the file ends up being on disk. The additional overhead is at least 5% even for a completely contiguous file because of the overhead of using the filesystem to find the file's blocks by scanning the inode indirect blocks and double indirect blocks. Art S. Kagel
Hi all, "Art S. Kagel" wrote: > > "Wile E. Coyote" wrote: > > > This is a common misconception. Informix Dynamic Server (though not SE) > opens ALL chunks that are NOT RAW in O_SYNC mode so that the write system > call will not return until the system buffers used by that I/O have been > flushed to disk. If you use IDS your data is ALWAYS SAFE. This is not the > problem. Excuse my ignorance. Wile