> -----Original Message-----
> From: Scott M. Ransom [mailto:[EMAIL PROTECTED]]
> Sent: Monday, April 24, 2000 6:13 PM
> To: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; Gregory Leblanc; bug1
> Subject: RE: performance limitations of linux raid
>
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>
> >> There's "specs" and then there's real life. I have never
> >> seen a hard drive
> >> that could do this. I've got brand new IBM 7200rpm ATA66
> >> drives and I can't
> >> seem to get them to do much better than 6-7mb/sec with
> either Win98,
> >> Win2000, or Linux. That's with Abit BH6, an Asus P3C2000,
> >> and Supermicro
> >> PIIIDME boards. And yes, I'm using an 80 conductor cable.
> I'm using
> >> Wintune on the windows platforms and bonnie on Linux to do
> benchmarks.
> >
> > I don't believe the specs either, because they are for the
> "ideal" case.
>
> Believe it. I was getting about 45MB/s writes and 14 MB/s reads using
> RAID0 with the 2.3.99pre kernels on a Dual PII 450 with two 30G
> DiamondMax (7200rpm Maxtor) ATA-66 drives connected to a
> Promise Ultra66
> controller.
>
> Then I moved back to kernel 2.2.15-pre18 with the RAID and IDE patches
> and here are my results:
>
> RAID0 on Promise Card 2.2.15-pre18 (1200MB test)
> ----------------------------------------------------------
> -------Sequential Output-------- ---Sequential Input-- --Random--
> -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
> K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
> 6833 99.2 42532 44.4 18397 42.2 7227 98.3 47754 33.0 182.8 1.5
> ***** *****
>
> When doing _actual_ work (I/O bound reads on huge data sets), I often
> see sustained read performance as high as 50MB/s.
>
> Tests on the individual drives show 28+ MB/s.
Sounds dang good, but I don't have any of those yet... When I can get a
1350 MHz proc, I'll grab a new machine an correlate these results for
myself. :-)
>
> The performance is simply amazing -- even during real work (at least
> mine -- YMMV). And best of all, the whole set-up (Promise card + 2X
> Maxtor drives only cost me $550....)
>
> I simply can't see how SCSI can compete with that.
Easy, SCSI still competes. It's called redundancy and scalability. It's
hard to get more than 4 (maybe 8 with a big system) IDE drives attached to
one box. That same thing is trivial with SCSI, and you can even go with far
more than that. Here's on example. At the office, I've got a single
machine with 4 internal, hot-swap drives, and two external 5 disk chassis
that are both full, as well as a tape drive, a CD-ROM, and a CD-RW. The
tape is about 3 feet away, and the drive chassis are more like 12,
everything is well withing spec for the SCSI on this machine. With IDE, I
couldn't get that much space if I tried, and I wouldn't be likely to have
the kind of online redundancy that I have with this machine. I'll admit
that this is the biggest machine that we have, but we're only taking care of
250 people, with about a dozen people outside of the Information Services
deparment who actually utilize the computing resources. Any remotely larger
shop, or one with competent employees, could easily need server that scale
well beyond this machine. I don't think that SCSI has a really good place
on desktops, and it's use is limited when GOOD IDE is available for a
workstation, but servers still have a demand for SCSI.
Greg
P.S. My employer probably wouldn't take kindly to those words, so I'm
obviousally not representing them here.
