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Subject: Re: Slow EGTBs

Author: Eugene Nalimov

Date: 13:46:10 01/16/03

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David, *fast* SCSI drive is noticeable faster than best IDE drive. Problem is
not only 15k or 10k rpm vs. 7.2k rpm. Problem is also seek time. On best IDE
drive I had seen it's something ~8-9ms. On *average* SCSI drive it's ~4-5ms.

More, I have Itanium 2 system with one SCSI drive with 320Mb/sec SCSI disk
drive, and one with "only" 160Mb/sec. And I regularly see the difference. Drive
with 320Mb/sec is really faster when I am doing something with tens of gigabytes
of data :-)

Thanks,
Eugene

On January 16, 2003 at 15:12:06, David Rasmussen wrote:

>On January 16, 2003 at 14:47:54, Robert Hyatt wrote:
>
>>On January 16, 2003 at 13:31:39, David Rasmussen wrote:
>>
>>>I do more or less the same thing as everybody else, when probing EGTB's, judging
>>>from the open source programs I've inspected. But I get a severe drop in NPS
>>>when the tables are probed heavily. Much more than other programs, from what I
>>>can see on ICC.
>>>
>>>What could be the course of this?
>>
>>Fast disks.  IE I am currently using 15K rpm, ultra-320 scsi drives, with six of
>>these 36 gig screamers running in a raid-0 (striped) manner, which is _really_
>>fast.
>>
>>If you are using an EIDE disk, performance is going to die.  Particularly if you
>>are
>>using 5400 rpm drives.
>>
>
>First of all, I'm not using 5400 rpm drives. Secondly, current IDE disks are not
>as bad as you think. Thirdly, all of the program I've compared with during games
>on ICC, where running on IDE disks, I would think.
>
>>
>>>I have the same order of number of probes as other programs as I can see on ICC.
>>>So my limiting of probes is not the problem. I only probe in the first couple of
>>>plys and if there have just been a change of material on the board. The harddisk
>>>I use is very fast. It is a Western Digital 80GB 7200 RPM with 8MB cache. So
>>>that shouldn't be the problem either. I use NTFS, not FAT, I don't know if that
>>>makes a difference, or file systems in general. I haven't done any serious
>>>testing of this on EXT2, EXT3, ReiserFS etc. But as far as I know, people are
>>>able to do this on Windows, so I must be able to do it too.
>>
>>that 7200RPM drive is double the rotational latency of a 15K drive.  The
>>bandwidth
>>is a small fraction of a hot ultra-320 SCSI drive.
>>
>
>I know it's slower, but very few people are not using disks comparable to mine,
>and they don't seem to have a problem. Disks such as yours are not strictly
>necesary, I would think. Maybe I'm wrong. Also, I still think you are
>underestimating the performance of current IDE drives.  I don't believe that
>fraction is very small.
>
>>You might try upping the egtb cache size significantly to avoid some I/O.
>>
>
>To how much, would you say? I tried going from 8MB to 64MB just now, and it
>didn't help at all. In fact, it was slower.
>
>/David



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