Re: Ebaying - Comparisons

From: UNIX admin (tripivceta_at_hotmail.com)
Date: 09/08/04 

Date: Wed, 8 Sep 2004 11:46:33 +0200

> I was (rather obliquly, admittedly) refering to the use of
> SCSI disks. IMHO, IDE disks do not belong in a server, with
> the sole exception of stuff that doesn't touch disks very oftne
> (e.g., a DNS server which caches everything in RAM).

Generally, I agree. If you want the top notch perf, you better fork out the
dough for SCSI. Although, if one knows what one is doing, there are tricks
& games one can play to squeeze decent perf out of ATA. It is a bit more
complicated than SCSI, but it is offset by dirt cheap hardware, and thus
very low costs.

Nowdays PC bucket motherboards come with two channel controllers. Add
another two controllers, two channels apiece, hook up all the disks as one
master per channel (preferrably using "cable select" with an UDMA ATA
cable), use VM and UFS journaling, and you'll be pushing 40MB/s or more.
And the disks are on different controllers doing DMA transfers.

I'd say that for ATA junk 40MB/s ain't too shabby, especially if you nail
120GB disks for peanuts. Hell, Ultra SCSI was pushing, what, 20MB/s?
Of course, SCSI has synchronous I/O and CTQ as well as robust error checking
and recovery, something ATA can only dream about.

With that crap out of the way, if you want a high perf server, Ultra320 SCSI
is the way, the light, the truth.

> Agreed, but I guess you have to look at their original design
> target. I always chuckle at so-called data cantres that piled
> high with tower case PCs...

That's not a data center. That's a bunch of bozos playing IT personnel.

Relevant Pages

  • Re: Moving rootvg drive failed?
    ... >>Lacking the SCSI Riser the 340 has a MCA scsi installed too. ... >>Now the machine started from disks, but went to frequent error messages ... > IMHO it is not a good idea, to recycle an AIX installation in a different ... > type of server with different devices by simply exchanging the disks. ...
    (comp.unix.aix)
  • Re: bios disk numbers and device names
    ... You can wire disks down in SCSI, not sure about ATA. ... That said if you run 5.x devfs makes this sort of thing MUCH less painful.. ...
    (freebsd-stable)
  • Re: [OT] SATA vs. SCSI
    ... > its getting converted to ata disks fairly rapidly as the scsi raid ... If you have disks dying every 2 weeks, ... batch of bad SCSI drives recently. ... > drives per server. ...
    (Debian-User)
  • [HPADM] EMC symmetrix alt pv link problem
    ... All the disks are ... On each server I have 2 scsi adapter cards providing alternate pv links to ... EMc have just reconfigured the box for 2 more luns. ...
    (HP-UX-Admin)
  • Re: SATA vs SCSI
    ... > We're looking at switching to Windows 2003 and buying another server to host ... complex answer I guess: is it still best to stick with SCSI ... SATA may look the same in some benchmarks, ... Seagate, or maybe new Hitachi, most of the disks may even be alive ...
    (comp.sys.ibm.pc.hardware.storage)