> -----Original Message----- > From: Mike A. Harris [mailto:[EMAIL PROTECTED] > Sent: Tue, March 11, 2003 9:54 AM > To: [EMAIL PROTECTED] > Subject: Re: hdparm settings > > > On Mon, 10 Mar 2003, Jesse Keating wrote: > > >> # grep USE_DMA /etc/sysconfig/harddisks > >> USE_DMA=1 > >> > >> # hdparm -t /dev/hdb > >> /dev/hdb: > >> Timing buffered disk reads: 64 MB in 1.18 seconds = 54.07 MB/sec > > > >This is different. It's setting an approved config file, > for Red Hat init > >scripts to parse, and set hdparm options. It is not using > hdparm directly on > >the disk. Some hdparm settings you can use, w/ little fear of data > >corruption. Some you can't. This is most likely what Arjan > was referring > >to. Arjan's statements were pretty vague, so take them as > that unless he > >clarifies a bit. > > I can clarify Arjan's statements a bit. Basically, in all modern > kernels, the kernel autodetects the hard disk's capabilities > itself, and sets the drive for the best performance > _automatically_ itself without any end user intervention. If for > any reason, a hard disk setting is _not_ enabled by the kernel, > it is because the kernel knows that that setting is not safe to > use. The kernel contains various blacklists/whitelists of known > bad/good hardware combinations, known motherboard chipset bugs, > and whatnot, and it sets the drive to enable the fastest transfer > rates for your hardware combination that is also "safe" to use.
Actually, I have one system that quite often freezes when DMA is enabled for the harddisk. Every time I install linux I have to disable DMA manually on it. > > If someone then goes and plays with hdparm settings, they may in > fact be force-overriding the kernel's safety mechanisms, and > enabling some setting that triggers a flaw in the drive, the > motherboard chipset, or some combination of the two, and that may > cause data corruption. > > Second guessing the hard disk settings that modern kernels > default the drives to is Russian Roulette. Some settings might > turn out to be harmless (or perhaps the kernel just ignores them > and you _think_ the change did something), while other settings > perhaps do change something (but have zero real effect on speed). > > Short Answer: Trust the kernel to do the right thing. > > > -- > Mike A. Harris ftp://people.redhat.com/mharris > OS Systems Engineer - XFree86 maintainer - Red Hat > > > > -- > Phoebe-list mailing list > [EMAIL PROTECTED] > https://listman.redhat.com/mailman/listinfo/phoebe-list > -- Phoebe-list mailing list [EMAIL PROTECTED] https://listman.redhat.com/mailman/listinfo/phoebe-list
