Date: Sun, 21 May 2000 19:01:42 +0200 (CEST) From: =?ISO-8859-1?Q?G=E9rard_Roudier?= <groudier@club-internet.fr> To: Kenneth W Cochran <kwc@world.std.com> Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: SCSI 2x-4x slower than IDE? Message-ID: <Pine.LNX.4.10.10005211811110.365-100000@linux.local> In-Reply-To: <200005211221.IAA01609@world.std.com>
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On Sun, 21 May 2000, Kenneth W Cochran wrote: > Hello -scsi, > > (Yes, the old SCSI vs IDE flamewar, but I'd like to avoid that, > thank you... :) What flamewar ? :) May-be you refer to IDE being reported fast for sequential access under stupid benchmarks but slow for really useful IO patterns. No flamewar needed here. :-) > This is related to FreeBSD because I'm considering these devices > for a FreeBSD box... :) A recent message on this list spoke to > this issue in general but I could use some info as to the > specifics, if possible. > > Partly on my recommendation, a freind of mine tried SCSI as a > proposed upgrade to his old IDE system. He is/was interested in > improving performance with sequential saves while editing & > cd-burning music (live recorded recitals). File sizes are in > the 10s & possibly 100s of mb. > > He got a Tekram DC-390U2W & an IBM Ultrastar DNES-318350. There > are/were a couple of other previous scsi peripherals (older IBM > hdd & a tape drive, I think) running on an Adaptec 2910. OS is > Win9x (not sure exactly which). The Tekram DC-390U2W uses a SYMBIOS 53C895 PCI-SCSI PCI-SCSI controller. This controller is as _good_ as Tekram drivers for the U2W board are pathologically _bad_. ;-) If your friend is using the Tekram driver, since it seems the SYMBIOS driver for Win95/98 does not recognize the board, things should not be so optimal, in my opinion. > What happened: Sequential saves with older scsi disk (vs older > ide) took twice as long, & sequential saves with new IBM took > twice as long as with older scsi disk. Hmmm... could the driver be incredibily bad or the new drives not having write caching enabled but old ones having write caching enabled ? (Or something too weird to guess about ...) Disk write caching option should be checked, in my opinion. > The file/save on the ide took about 4 minutes, the "old" scsi > disk (an IBM) took 8 minutes & the new IBM DNES took 15m:21s. > His IDE is not even the newer, supposedly faster, stuff. 15 minutes is probably time enough for writing more than 10 GB to the IBM disk. Something seems extremally wrong with the system, unless dozens of GB are actually saved, which I guess is not the case. > I've always read & heard that Unix in general & FreeBSD more > specifically perform much better with scsi hdds than ide > (better, more intelligent i/o, "multithreadedness," > multitasking, etc.), & that this might not be the case with > Win9x, due to its "single-threaded" nature, but would that > account for this magnitude of performance difference? Speaking about SCSI in general and SYMBIOS controllers in particular, I think that FreeBSD gives the best possible support (Btw, we are not using drivers from Tekram for DC-390/U/F/U2W/U2B controllers). > I've always been quite satisfied with scsi & unhappy with ide > for systems I've built & used (Unix, Linux, *BSD). 2 questions: > > 1. What's going on "here" in M$/Win9x? This seems off-topic here. You should suggest your friend to give a try with FreeBSD and may-be pain somewhere he will have compared to his preferred O/S regarding SCSI IO performances. :-) > 2. What does this imply (or not imply) for FreeBSD? In my opinion, this does imply _nothing_ for FreeBSD, neither for Linux by the way (since I also maintain Symbios drivers for Linux:) ). > FAQ, -doc, & other reference pointers are, of course, quite welcome. :) The access method is called 'CAM' and the driver you want to use for the SYMBIOS 53C8XX based controllers is called 'sym'. The 'sym' driver appeared in FreeBSD 4.0 but is also available for 3.X. There is another driver called 'ncr' that also supports the SYM53C895. Regards, Gerard. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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