Hm, this seems to be a little summary of the mails and discussions who
had taken part of the list the last weeks.
Well, the corruption of data without being noticed by the parity
function is one secret; the other one is why this happened...
The comment: "99%..." is garbage, because it sounds like my colleague;
he had bad experiences years ago and since that time all PC stuff is
garbage...
By the way, HP uses Adaptec 2940-UW controllers on their machines sold
under the alias "k-machines" - pretty good PC stuff. Yes, I am working
on HP machines, but they are rather expensive and HP also uses Intel
processors, Adaptec controllers (as I said) and for example Seagate
disks; of course the disks are wearing the HP logo for which they are
twice times more expensive than normally...
I prefer "PC garbage" because it provides more flexibilty and is less
expensive; for sure, some applications should run on "professional"
servers, but what about the large number of Linux-(PC)Servers serving
internet data?
At last I want to thank those people who tried to solve "my" problem
(corrupted data, timeouts and so on); I, *YOU* "solved" it (the machine
is running fine now for about 4 or 5 days - knocking on wood) and the
database problem (corrupted tablespaces at 8k blocking size) belongs to
the Oracle8 software.
Thank you again for your help, Dietmar
Francisco Jose Montilla wrote:
>
> Hi, I happen to came across a couple of statements that somewhat
> involves the use of RAID, statements that I believe are not absolutely
> correct, if not false, or half truths.
>
> Both come from sources I believe to be respectable, but.. who
> knows...
>
> First: On Philip Greenspun's "Philip and Alex's Guide to Web
> Publishing", http://www.photo.net/wtr/thebook/server.html, anyone reads:
>
> -----------
> [...]
> Keep in mind that 99 percent of PC hardware is garbage. A friend of mine
> was a small-time Internet service provider. He was running BSDI, a
> not-quite-free Unix, on a bunch of PC clones. A hard disk was generating
> errors. He reloaded from backup tape. He still got errors. It turned out
> that his SCSI controller had gone bad some weeks before. It had corrupted
> both the hard disk and the backup tapes. He lost all of his data. He lost
> all of his clients' data.
>
> Lesson 1: You are less likely to lose with a SCSI controller designed
> by a real engineer in the Hewlett-Packard Unix workstation division than
> you are with one thrown in on a $49 sound card.
>
> Lesson 2: Mirrored disks on separate SCSI chains. Period.
> ------------
>
> I know the HP part is gonna make Dietmar's delights :). Apart from
> that, I wonder:
>
> - Doesn't SCSI controllers use parity? (Although you have to
> enable it, of course)
>
> - I agree on using two *controllers* (not two channels on the same
> controller) gives appropiate redundancy if one of they go mad, but
> nonetheless, although we use only one, shouldn't data corruption be
> detected by the controller parity? One step further, how will the soft
> RAID code handle this? does it have some heuristics to detect that, or is
> completelly the task of the controller and imposible for soft RAID to
> detect that?
>
> Second: I was wandering by PenguinComputer site, after looking at
> that 8way Xeon beast (http://www.penguincomputing.com/8000.cgi), and
> following the link related to RAID, (a good source of somewhat biased but
> good theoretycal info) on the FAQ section I found
> (http://www.penguincomputing.com/RAID.html)
>
> ----------
> Why would I want a two channel RAID card for RAID one?
>
> By putting each harddrive on a separate channel, you can ensure that even
> if a cable or terminator on one channel were to go bad, the system would
> continue to function.
>
> When hot-swapping a harddrive, the RAID card must temporarily stop the
> SCSI channel the drive is attached to. If the other drive in a RAID one
> array is connected to a different channel, the computer can operate
> completely normally during the hot-swap.
> ------------
>
> I agree completely with the first statement. But the second sounds
> somewhat odd to me. I can hotadd or hotremove a disk on linux with sw RAID
> and a non-hot swappable capable controller, maybe this is another feature
> of sw RAID over hw RAID?
>
> greetings,
>
> *****---(*)---**********************************************---------->
> Francisco J. Montilla Systems & Network administrator
> [EMAIL PROTECTED] irc: pukka Seville Spain
> INSFLUG (LiNUX) Coordinator. www.insflug.org - ftp.insflug.org
--
"Don't fear the Gates" (a little like Blue Oyster Cult)
Dietmar Stein, Systemadministrator UNIX/Linux
[EMAIL PROTECTED], [EMAIL PROTECTED]
