Re: DF <> SE Compatibility, Size compatibility with Debian, /HOME & other noobness?
hi Bram,
if DF means "high voltage differential" (what i suppose it means):
http://www.pcguide.com/ref/hdd/if/scsi/protDiff-c.html
-- snip --
Warning: Since single-ended and HVD SCSI use very different voltage
levels, they are incompatible at the electrical level. You should not mix
single-ended (or low voltage differential) devices with high voltage
differential SCSI devices on the same bus. If you do, actual physical
damage could result--this is one of those cases where actually smoking
your hardware is a distinct possibility, because of the high voltages that
might be sent to the single-ended or LVD devices! To compound the matter,
the cables and connectors used for single-ended and differential SCSI look
the same.-- snip --
you have been warned.
Differential uses the Ground Lines of Single Ended.
Differential drives with very high voltage are no good for SE controllers.
Differential Hard disk in SE slot will at least burn up the scsi
controller if not the whole printed circuitry in the box.
please consider this.
Smartelectronix - Bram said:
> Hello,
>
>
> 1. I was wondering if DF-disks work in SE slots.
> All the disks are marked on the bottom with
> a caution against just this ("do not use in SE slot"),
> but isn't DF backwards compatible?
what you mean is LVD.
low voltage differential.
it is "sensing and disabling" the LVD transmission if ANY single ended
disks/cdroms/tapes are on the "shared bus".LVD starts, where WIDE ULTRA2 Single Ended Scsi ends:
Differential FAST WIDE=20MB/s can use cables up to 25meter (good for
libraries and external storage shelves, the 735/125 also uses FWD)
Single Ended Narrow=5-10MB/s (used internally and for the 7xx workstations)
disk size 500mb - 4gb normally
Single Ended FAST WIDE=20MB/s 6 meter (used in recent workstations)
you will find disks sized about 4gb
Single Ended WIDE ULTRA= 40MB/s 3 meter external cables (internal scsi of
the C200 for example)disk size 4gb-9gb normally
Single Ended WIDE ULTRA2=80MB/s 3 meters approx (fast, faster, ultra2 :-)
you can find 18gig disks with ultra2 (also SCA connector)
Low Voltage Differential WIDE ULTRA3=160MB/s (up to 320MB/s currently)
used in pci controllers (adaptec) and high end up to date workstations
disk size 18gb to 36 or 72gb
LVD Wide Ultra3 is the standard nowadays.
i have from single ended to ultra2 with HVD, SE
i also have SE disks with SCA connectors, 50narrow or 68wide
> The slots in the 'server-casing' itself are SE, the slots
> in the 'drive-arrays' are DF, so it seems logical to
> install everything on the DF arrays instead of the
> disks in the server-slots.
> I only noticed yesterday that the slots in the 'server-casing'
> are SE, which is half as slow!
right.
Hewlett-Packard used FWD very often - Fast Wide Differential, with 20MB/s
transfer speedSE is normally between 10-20MB/S (it is only narrow normally)
>
> 2. I've been having big problems using larger disks
> for installing Debian-HPPA on it, but last night
> I at last succeeded in installing it on the
> smallest disk in the server (2GB).
>
> Are there known issues w/ installation on large (9GB)
> disks?
maybe you should check your palo partition and / partition
what says "boot pri"?
can`t find it?
or is palo hanging?
"boot pri isl" or "boot pri ipl" should drop you into the palo
or the ISL of hp-ux if it is still on the disk
>
> 3. how do I set /HOME to a different disk?
> Using PALO + boot-parameters : "HOME=/dev/whatever" ?
dunno, why do you need this?
i could take a look this evening in the palo manpage on my box at home
>
> 4. last but not least. For a server with 512Mb RAM, what
> is the recomenended swap-size? And, should I put the swap
> on a different disk?
swap on different disks is always good.
more spindles, more speed :-)
i would recommend RAM * 1.5 = swap, depending on your software
on my 512mb machine, i remember having 3 disks with each 500mb swap
it does mainly heavy compiling and i am very satisfied with the speed
(it has IBM DCAS disks, 3x4.5gig ultra wide running rocksolid at 40MB/s)
>
>
> kind regards + thanks a lot for helping this newbie,
have a nice day,
Alex
>
>
> - bram
>
> PS: "welcome to debian" was quite nice to see :-)
>
> --
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>
>
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