another error with md malloc based fs

[Kevin Oberman]

> Date: Thu, 22 Mar 2007 23:04:16 +0100
> From: "Michael Schuh" <michael.schuh at gmail.com>
> Sender: owner-freebsd-stable at freebsd.org
> 
> Hi,
> first i have 2GB of RAM, there are be 1,6G free
> so it should enough toi make the following:
> 
> # mdconfig -a -t mallo -s 750m -u 0
> # bsdlabel -w /dev/md0
> # bsdlabel -e /dev/md0 (create "a" slice to use all free respective first 16
> blocks)
> # newfs -O2 -U /dev/md0a
> mount /dev/md0a /mnt
> # cd to_a_place/with/650MB_of_data/
> # tar -cf - |( cd /mnt/; tar -xf -)
> after ~256MB transferred i get following errors, and the system crashes
> horridble....  first it doesnt react of anything, then it does silently
> reboot
> without a shutdown.......leaves all unclean....
> 
> extract from all.log
> Mar 22 22:08:14 flying-dutchman kernel:
> g_vfs_done():md0a[WRITE(offset=686899200
> , length=131072)]error = 28
> Mar 22 22:08:14 flying-dutchman kernel:
> g_vfs_done():md0a[WRITE(offset=687030272
> , length=131072)]error = 28
> Mar 22 22:08:14 flying-dutchman kernel:
> g_vfs_done():md0a[WRITE(offset=687161344
> , length=131072)]error = 28
> Mar 22 22:08:14 flying-dutchman kernel:
> g_vfs_done():md0a[WRITE(offset=687292416
> , length=131072)]error = 28
> 
> 
> Any impressions, suggestions or limitations for md with malloc?
> This errors occures also if i request to reserve the space by creation....
> 
> thanks
> 
> regards
> 
> michael
> 
> -- 
> === michael-schuh.net ===
> Michael Schuh
> Preußenstr. 13
> 66111 Saarbrücken
> phone: 0681/8319664
> mobil:   0177/9738644
> @: michael.schuh at gmail.com

Old, old joke:
Patient: Doctor! It hurts when I do this!
Doctor: Don't do that.

This is a well known issue with malloc backed md disks. Use swap backed
ones. They will be the default in V7. They have all of the advantages of
malloc backed mds without the possibility of eating all available memory
and crashing the system.

malloc backed md disks are very dangerous and should only be used in
special circumstances and with great care.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751
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