On Mon, Dec 29, 2003 at 11:56:56AM -0500, Linux Rocks! wrote: > : A poorly kept secret is that HDs have things like bad sectors all the time > : and that the drives themselves have known for ages how to recognize > : sectors that are going bad before they do. When this happens, they > : silently reroute your bits to unused sectors they do not advertise as > : actually being available. This screws with things like interleaving, but > : nobody interleaves for a speed boost anymore. (Why? RAID finally really > : does mean inexpensive disks...) Anyway, you only see bad blocks when the > : drive runs out of spare sectors. > > True, those are called "reserve sectors, typicly drives have 1% reserve > sectors to "replace" bad sectors on the fly... > I dont understand how this effects interleaving... As i understand it, > Interelaving is the space between the tracks (or is that cylinders). > Anyway...
An interleave is a re-ordering of sectors. Generally, it was assumed that most controllers can't write two adjacent sectors and you have to wait a whole revolution of the drive to write the next one. Adding an interleave of 2 or 3 (read every odd or every third sector) had the potential to really speed things up. Interleaves were drive, controller, and on VLB and PCI machines, bus-speed specific. Some systems could handle 1:1 just fine, others did better with 1:2 or 1:3 with the same drive. Having to seek to a reserved sector kinda breaks the smooth write process (and the smooth read for that matter), so that's a factor. I'm told that ESDI drives lack reserved sectors by design for this reason. No way to verify this last point though. > : Low-level formats of drives are scary undertakings. Usually when I've > : needed to do it, it was because the drive was damaged. Usually, the > : reformat doesn't help matters even a little bit. Just a word of warning. > > Ive done this many times... its really not so scary if you use the right > tools... I think Ive broken 1 out of 50 drives or so, and ive recoverd the > other 49 (ok, some of those drives only worked for a day or so, but many > lived happy lives for many years following...) Usually, having to break out the utility (or rather, go digging for it on google or the manufacturer's website) is a sign of impending doom. It's like installing Windows 98. As soon as you reach for the software, you know you're about to do something dangerous and undesirable. You just know you're going to have even bigger problems just as soon as you lay the thing aside and try to do anything useful with the hard drive. ;) > You can use older bios low level formatting if you know all the right > settings.. letting it guess can be risky though... I recommed using > manufacturers LLF utility over bios LLF utilities. I have only ever used a BIOS formatting with SCSI because SCSI controllers of old had different schemes for the format of the drive based on who made the controller. Some settings still exist that cause you to be suddenly unable to access a SCSI drive such as whether the SCSI BIOS should try to make the drive work in DOS or not. _______________________________________________ EuG-LUG mailing list [EMAIL PROTECTED] http://mailman.efn.org/cgi-bin/listinfo/eug-lug
