Messages in this thread | | | Date | Thu, 13 Dec 2007 17:27:39 -0500 | From | Bill Davidsen <> | Subject | Re: Kernel 2.6.23.9 / P35 Chipset + WD 750GB Drives (reset port) |
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Tejun Heo wrote: > Bill Davidsen wrote: > >> Jan Engelhardt wrote: >> >>> On Dec 1 2007 06:26, Justin Piszcz wrote: >>> >>>> I ran the following: >>>> >>>> dd if=/dev/zero of=/dev/sdc >>>> dd if=/dev/zero of=/dev/sdd >>>> dd if=/dev/zero of=/dev/sde >>>> >>>> (as it is always a very good idea to do this with any new disk) >>>> >>> Why would you care about what's on the disk? fdisk, mkfs and >>> the day-to-day operation will overwrite it _anyway_. >>> >>> (If you think the disk is not empty, you should look at it >>> and copy off all usable warez beforehand :-) >>> >>> >> Do you not test your drive for minimum functionality before using them? >> > > I personally don't. > > >> Also, if you have the tools to check for relocated sectors before and >> after doing this, that's a good idea as well. S.M.A.R.T is your friend. >> And when writing /dev/zero to a drive, if it craps out you have less >> emotional attachment to the data. >> > > Writing all zero isn't too useful tho. Drive failing reallocation on > write is catastrophic failure. It means that the drive wanna relocate > but can't because it used up all its extra space which usually indicates > something else is seriously wrong with the drive. The drive will have > to go to the trash can. This is all serious and bad but the catch is > that in such cases the problem usually stands like a sore thumb so > either vendor doesn't ship such drive or you'll find the failure very > early. I personally haven't seen any such failure yet. Maybe I'm lucky. >
The problem is usually not with what the vendor ships, but what the carrier delivers. Bad handling does happen, "drop ship" can have several meanings, and I have received shipments with the "G sensor" in the case triggered. Zero is a handy source of data, but the important thing is to look at the relocated sector count before and after the write. If there are a lot of bad sectors initially, the drive is probably a poor choice for anything critical. > Most data loss occurs when the drive fails to read what it thought it > wrote successfully and the opposite - reading and dumping the whole disk > to /dev/null periodically is probably much better than writing zeros as > it allows the drive to find out deteriorating sector early while it's > still readable and relocate. But then again I think it's an overkill. > > Writing zeros to sectors is more useful as cure rather than prevention. > If your drive fails to read a sector, write whatever value to the > sector. The drive will forget about the data on the damaged sector and > reallocate and write new data to it. Of course, you lose data which was > originally on the sector. > > I personally think it's enough to just throw in an extra disk and make > it RAID0 or 5 and rebuild the array if read fails on one of the disks. > If write fails or read fail continues, replace the disk. Of course, if > you wanna be extra cautious, good for you. :-) > > -- Bill Davidsen <davidsen@tmr.com> "Woe unto the statesman who makes war without a reason that will still be valid when the war is over..." Otto von Bismark
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