On Monday 10 February 2003 11:05 pm, vatbier wrote: > civileme <[EMAIL PROTECTED]> wrote: > > WD drives of the generation you are using do not calculate that same > > CRC for comparison--they store it in their big 600-byte sectors along > > with the 512 bytes of data. They may calculate the first in a series > > of writes, but not all. > > > >The drive is safe enough run at udma2 (33Mhz and 32 byte CRCs) or > > > > If you cannot put a better drive in that box, a 40-pin cable could > > make a big difference for the safe operation, to force 33MHz or lower > > transfer speed. > > Thanks! > I had already read that WD and UDMA5 give problems but my hard drive > WD400BB-32CXA was bought in april 2002. Were can I find the generation > info that my drive has no good CRC checking at UDMA3,4,5? I searched the > Western Digital website (wdc.com) but they don't give that kind of > information. Do the new WD400BB drives do correct CRC checking? > > You say "They may calculate the first in a series of writes, but not > all.": where can I find that kind of insight info, I searched the net > but apart from some of your postings haven't found much else. > > I don't have a 40-pin cable. If I use the hdparm command > hdparm -k1 -d1 -X66 /dev/hda (66:UDMA2), would this give the same > effect? Can changing the UDMA setting with hdparm give problems/errors? > I also downloaded from the WDC website Data Lifeguard Tools that can > change the udma setting on the hard drive itself. If I used this to > change the UDMA to 2, would my linux have no problems with this (I'm a > a little scared to use hdparm or WDC tools, in "man hdparm" they state > "Use with extreme caution! This feature includes zero protection for > the unwary, and an unsuccessful outcome may result in severe filesystem > corruption!") ? > > How can I prevent CRC errors? Can an IDE-cable suddenly become bad, or > experience interference, I read about twisted cables, ... > "The HDD should NOT be mounted near the power supply due to fan issues. > The fan in the supply causes the HDD to misinterpret CRC-checksums and > produces CRC-errors. Also, high-speed CD drives should not be near the > HDD" : fan causing CRC-errors? CD drives ? > > How much slower is UDMA2 than UDMA5? (hdparm -t), You said somewhere > that the performance does not differ much?
The X66 is safe to use as you have described it. What is dangerous is overdriving. Win98 isn't going to give you more than what it has drivers for, so the DataLifeguard should not be necessary. Also, IIRC, DataLifeGuard phones home and gives you warning if your drive is about to fail (and it works on non-WDs too). Yes you are not going to find much info on the WD drive and their strategy to produce cheap drives ... These days they say they are fully compatrible with advanced UDMA, but offer no details, which is itself suspicious. The last time I exchanged emails with Andre Hedrick, we were still experiencing problems, but I have been out of the loop for some time. I wrote a program for 8.0/8.1 called drakopt which exhaustively tested options under hdparm for a given rig of drives, and set up the optimization. On some of the rigs the Crashtesters had, when the drive was set to highest rated speed and another drive was on the same channel there would be crosstalk errors. That was not supposed to happen either; only one drive on an IDE channel is supposed to be on at a time, but it was happening when one of a pair was a WD. (As an aside from this, if you have enough IDE channels to do it, put one hard drive per channel and use the other (slave) side for CDROM or Zip or whatever, not only to avoid crosstalk but for efficient operation.) As for the variance of speed, consider this... The PCI bus is 33MHz and 32 bits wide--the data transfer cable for IDE is 16 bits wide and up to 133Mhz, already twice what the PCI bus can handle, so the "speed" has to be burst mode cause there are controllers for IDE at 133MHz which plug into the PCI bus. Overwhelmingly, the consideration has to be with the disk itself, where data spins on or off of it at 1/60 the rate of the interface, approximately. Buffering helps, and lookahead helps, and elevator tuning helps (yes check out man elvtune), but the mechanical end of things is very slow compared to the rest of it. To increase disk speed, the most productive approaches are: *Increase spin rate *Software or hardware driven striping (RAID0 RAID4 RAID5) with multiple disks, especially if chunk size is controlled so that the switch to a different drive most frequently occurs when the first drive would need to step. The pinout on IDE cables is available here: http://www.howstuffworks.com/ide3.htm Of course with like 30 nanoseconds pulse width and data transfer on rising and falling edges, we are talking about something where a secondary cosmic ray is a significant noise source. Not much charge moves on those cables at the interface voltage in that time span. At this address http://www.linux-ide.org/ata.html You can download an ATA66 disable utility (windows compatible) for your WD. I have heard of the WD Raptor series with a 10,000 rpm spin rate, but I think I will stick to the others until WD does full disclosure on how its CRC works. Civileme
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