2004-04-07 13:23:37

by Gewj

[permalink] [raw]
Subject: A puzzling thing about RAID5: syslogd write the log success but another process can not read the /var/log/messages

hammm,tonight is funny because I got a puzzling thing just as....

my setup is a two-scsi-disk raid5 configuration...
(Linux version 2.4.18-18.7.xsmp (Red Hat Linux 7.3 2.96-112)) #1 SMP Wed
Nov 13 19:01:42 EST 2002)
it work well for a long time, but now I found some day early one of the
scsi disks failed, and I found out
that that time syslogd restarted(why??) and it could write log infor to
log file successfully.
but at the same time , another process(named such as B,run by root) can
not read
the /var/log/messages,or what's more exactly, the messages file was look
like empty to B then.
(of course, the syslogd write log infor to /var/log/messages )

I wonder that if syslogd write the log infor to the well-work scsi disk
, but the process B
read the /var/log/messages from the crashed scsi disk,which cause it
just like a empty file.

yes, it is quite unbelievable. but can some one show me a clue to this
puzzling problem?
What is the proper course of this action?











2004-04-07 14:52:31

by Lars Marowsky-Bree

[permalink] [raw]
Subject: Re: A puzzling thing about RAID5: syslogd write the log success but another process can not read the /var/log/messages

On 2004-04-07T21:24:01,
Gewj <[email protected]> said:

> hammm,tonight is funny because I got a puzzling thing just as....
>
> my setup is a two-scsi-disk raid5 configuration...

Impossible. RAID5 requires at least three disks.


Sincerely,
Lars Marowsky-Br?e <[email protected]>

--
High Availability & Clustering \ ever tried. ever failed. no matter.
SUSE Labs | try again. fail again. fail better.
Research & Development, SUSE LINUX AG \ -- Samuel Beckett

2004-04-07 23:13:33

by NeilBrown

[permalink] [raw]
Subject: Re: A puzzling thing about RAID5: syslogd write the log success but another process can not read the /var/log/messages

On Wednesday April 7, [email protected] wrote:
> On 2004-04-07T21:24:01,
> Gewj <[email protected]> said:
>
> > hammm,tonight is funny because I got a puzzling thing just as....
> >
> > my setup is a two-scsi-disk raid5 configuration...
>
> Impossible. RAID5 requires at least three disks.

Wrong. RAID5 works fine with just two drives. Try it.

NeilBrown

(I admit that there isn't a lot of point doing raid5 with two drives
as raid1 should provide identical functionality with better
performance, but it makes an interesting base-line for performances
tests on N-drive arrays).

2004-04-09 01:49:19

by Gewj

[permalink] [raw]
Subject: Re: A puzzling thing about RAID5: syslogd write the log success but another process can not read the /var/log/messages

thank for your comments

I should say that this question maybe end up without any reasonable result,
the system is now work well , I have give up investigating this problem
any more.
maybe the question is just cause by the RAID card crash.

Neil Brown wrote:

>On Wednesday April 7, [email protected] wrote:
>
>
>>On 2004-04-07T21:24:01,
>> Gewj <[email protected]> said:
>>
>>
>>
>>>hammm,tonight is funny because I got a puzzling thing just as....
>>>
>>>my setup is a two-scsi-disk raid5 configuration...
>>>
>>>
>>Impossible. RAID5 requires at least three disks.
>>
>>
>
>Wrong. RAID5 works fine with just two drives. Try it.
>
>NeilBrown
>
>(I admit that there isn't a lot of point doing raid5 with two drives
>as raid1 should provide identical functionality with better
>performance, but it makes an interesting base-line for performances
>tests on N-drive arrays).
>
>-
>To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>the body of a message to [email protected]
>More majordomo info at http://vger.kernel.org/majordomo-info.html
>Please read the FAQ at http://www.tux.org/lkml/
>
>
>