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- Re: kernel parms & RAW disk I/O
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11-19-2000 03:06 AM
11-19-2000 03:06 AM
kernel parms & RAW disk I/O
I see DBC_MIN/MAX_PCT, BUFPAGES, NBUF control how unix manages caching for disk I/O. Under the heading "filesystem I/O".
My system is a database server, accessed over the network, so very little "filesystem" I/O takes place, but a boat load of RAW disk I/O.
Do these parameters affect RAW I/O?
My system is a database server, accessed over the network, so very little "filesystem" I/O takes place, but a boat load of RAW disk I/O.
Do these parameters affect RAW I/O?
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11-19-2000 06:02 AM
11-19-2000 06:02 AM
Re: kernel parms & RAW disk I/O
Immediate reporting will affect raw I/O as it tells the disk to accept write requests and report that they are already completed. This is not recommended unless *all* the disks on the system are backed up with a battery so that pending writes from the disk's RAM will be completed.
You can also look at the scsictl man page to selectively enable immediate reporting on a disk by disk basis. This will require a technical reference manual for the disk(s).
Generally, raw I/O performance is 100% controlled by the application. Popular database programs offer a lot of choices to increase buffer sizes, keep indexes and hash tables in RAM, etc. Simple rule: maximize RAM usage by the database program (and think several gigabytes for CPU RAM).
Bill Hassell, sysadmin
You can also look at the scsictl man page to selectively enable immediate reporting on a disk by disk basis. This will require a technical reference manual for the disk(s).
Generally, raw I/O performance is 100% controlled by the application. Popular database programs offer a lot of choices to increase buffer sizes, keep indexes and hash tables in RAM, etc. Simple rule: maximize RAM usage by the database program (and think several gigabytes for CPU RAM).
Bill Hassell, sysadmin
The opinions expressed above are the personal opinions of the authors, not of Hewlett Packard Enterprise. By using this site, you accept the Terms of Use and Rules of Participation.
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