Messages in this thread | | | Date | Tue, 25 Sep 2001 12:42:31 +0200 | From | Matthias Andree <> | Subject | Re: [PATCH] 2.4.10 improved reiserfs a lot, but could still be better |
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On Mon, 24 Sep 2001, Nicholas Knight wrote:
> It's a very remote possability of failure, like most instances where > write-cache would cause problems. Catastrophic failure of the IDE cable > in mid-write will cause problems. If write cache is enabled, the write > stands a higher chance of having made it to the drive before the cable > died, with it off, it stands a higher chance of NOT having made it > entirely to the drive.
Cables don't suddenly die without the help of e. g. your CPU fan.
> For most drives, I don't know for sure if they'd finish the write > that's now sitting in their cache, but I expect higher quality drives > (such as our IBM drives) definitely would. Infact I may even be willing > to test this later (my swap partition looks like it wants to help :)
Drives would not write incomplete blocks.
> > It may be an implementation problem in our IBM drives which ship with > > their write caches enabled, someone please do this test on current > > Fujitsu, Maxtor or Seagate IDE drives or with different controllers. > > Either Maxtor or Western Digital share very close designs to IBM > drives, I belive they had some sort of development partnership. I'm not > sure if it was Maxtor or WD.
The Western Digital 420400D (20 GB, 5400/min) and its 7200/min brother with 18 GBs were IBM disk drives, supposedly, but the WD ...AA/BB drives and whatever else there was looked some different from IBM drives.
> > Why are disk drives slower with their caches disabled on LINEAR > > writes? > > Maybe the cache isn't doing what we think it is?
Maybe. A monitor software or debug mode would be good to see when writes are scheduled and which blocks are written (I need to ask a friend of mine who hacked ll_rw_blk.c on a different purpose for his diploma thesis, maybe his code is valuable to figure things out.)
> Does anyone have contacts at IBM and/or Western Digital? Something's > up... The 256MB write with write-cache off was going at 5.8MB/sec, and > with it on it was going at 14.22MB/sec (averages). One interesting > thing, the timings are showing a pretty consistant but tiny increase in > sys time with write caching on.
I also saw that here, but again, it's basically the same hardware.
-- Matthias Andree
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