From mboxrd@z Thu Jan 1 00:00:00 1970 From: bqt@update.uu.se (Johnny Billquist) Date: Tue, 24 Apr 2018 01:44:06 +0200 Subject: [TUHS] /dev/drum In-Reply-To: References: Message-ID: <9a5e49bb-f235-4b87-445b-1532d8facd2f@update.uu.se> On 2018-04-24 01:30, Grant Taylor wrote: > On 04/23/2018 04:15 PM, Warner Losh wrote: >> It's weird. These days lower LBAs perform better on spinning drives. >> We're seeing about 1.5x better performance on the first 30% of a drive >> than on the last 30%, at least for read speeds for video streaming.... > I think manufacturers have switched things around on us. I'm used to > higher LBA numbers being on the outside of the disk. But I've seen > anecdotal indicators that the opposite is now true. That must have been somewhere in the middle of history in that case. Old (proper) drives had/have track 0 at the outer edge. The disk loaded the heads after spin up, and that was at the outer edge, and then you just locked on to track 0, which should be near. Heads had to be retracted for the disk pack to be replaced. But this whole optimization for swap based on transfer speeds makes no sense to me. The dominating factor in spinning rust is seek times, and not transfer speed. If you place the swap at one end of the disk, it won't matter much that transfers will be faster, as seek times will on average be much longer, and that will eat up any transfer gain ten times over before even thinking. (Unless all your disk ever does is swapping, at which time the heads can stay around the swapping area all the time.) Which is also why the file system for RSX (ODS-1) placed the index file (equivalent of the inode table) at the middle of the disk by default. Not sure if Unix did that optimization, but I would hope so. (Never dug into that part of the code.) Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt at softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol