> On Saturday, March 02, 2002 06:55:24 PM +0300 Oleg Drokin <[EMAIL PROTECTED]> wrote:
>> Hello! >> >> On Fri, Mar 01, 2002 at 07:16:08PM +0100, Matthias Andree wrote: >>> I have some observation here that I cannot explain to myself. >>> It seems as though ReiserFS impaired my throughput on 650 MB files, >>> while ext3fs on the same drive did not. >> Known problem. >> >>> drive to hold images for writing CDs, /dev/sdb4, formatted with >>> reiserfs, and, because tail packing is pointless anyhow, mounted with -o >>> notail. >> Tails are not used for files bigger than 16k >> >>> However, when writing to an ATAPI 16x CD writer, the buffer ran empty, >>> triggering burnproof support. I then ran zcav to figure how fast the >>> drive itself was, and /dev/sdb ranged from 7.9 to 4.8 MB/s, no problem >>> here. When I read a CD-Image with dd (tried default block size and >>> bs=1048576), I only got 1.9 MB/s, evidently not sufficient to keep >>> feeding the CD-writer (16x needs 2.4 MB/s). I then nuked the whole disk, >>> reformatted it with ext3fs, everything is fine now, dd to the CD-Image >>> gives me 7.8 MB/s with bs=1M. >> >>> Does any of the *pending patches address this problem? I observed this >>> on several kernel versions, 2.4.14, 2.4.16, 2.4.19-pre1-ac2. >> >> This is a known problem. I and Chris are working on it exactly right now. >> This is a problem related to the fact that metadata is located on the other >> side of disk then the actual data. > I would not say that speeds this bad are a known problem. 1.9MB/s is > much too slow. Is that FS very full? Fragmentation is the only thing > that should be causing this. > -chris Even with 'heavy' fragmentation this is quite low. A quick benchmark of my 5400rpm 80GB disk gave me an average on 30MB/s. However, when simulating large fragmentation (10 000+ fragments on a 1GB file) I get about 2MB/s. Is DMA, unmask IRQ, read ahead and similar activated? //AW
