Read Ahead Cache

[Eckert_2]

We have L2000 (HPUX11i, Oracle with 2GB-Datafiles) connected via FC (A6795A) with IBM FASTT700. We want to improve the Backup-Performance by setting the kernel parameter vxfs_max_ra_kbytes. How can I calculate the right value?

[G. Vrijhoeven]

Hi,

This tunable vxfs_max_ra_kbytes, along with other "read-ahead" tunables vxfs_ra_per_disk and vx_fancyra_enable, has been obsoleted in HP-UX 11i Version 2 and is replaced by the filesystem tunable read_ahead. For more information on the VxFS file system tunables see vxtunefs(1M) .

check:

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B2355-60103/B2355-60103_top.html&con=/hpux/onlinedocs/B2355-60103/00/42/4212-con.html&toc=/hpux/onlinedocs/B2355-60103/00/42/4212-toc.html&searchterms=vxfs_max_ra_kbytes&queryid=20041018-071902

For more info.

Regards,

Gideon

[RAC_1]

In addition to Deodon's comment, check following doc. This discusses, the parameter in details.

http://www.docs.hp.com/hpux/onlinedocs/5576/JFS_Tuning.pdf

[G. Vrijhoeven]

Hi again,

discart my first reply, that was for 11.22 not for 11.11.

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/TKP-90202/TKP-90202_top.html&con=/hpux/onlinedocs/TKP-90202/00/01/175-con.html&toc=/hpux/onlinedocs/TKP-90202/00/01/175-toc.html&searchterms=vxfs_max_ra_kbytes&queryid=20041018-074743

Regards,

Gideon

[Eckert_2]

I have seen, there is no way to calculate the value, only try step by step.