RAID levels & logging
2007-12-25 10:18:00
We have a SPARC2000 with 4 SPARCstorage arrays (240GB) running
Solaris 2.5 and Volume Manager 2.1.1. The SPARC2000 will be a
database server with lots of reads and writes to Raw partitions.
1) Is RAID5 or Striping&Mirroring better from performance and
recovery point of views?
2) If we decided to go with "Striping&Mirroring", is it essential
to allocate space for Logging? If we choose NOT to do logging,
how long would it take for all the mirrors to resync if a system
failure occurs? Will the resync of mirrors occur every time I
need to shutdown or reboot the server?
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Responses:
1) Most of the people who responded advised against RAID5 and said
that striping&mirroring should perform better and is easier to
recover than RAID5.
2) I had received conflicting answers about whether to use "Dirty
Region Logging" or not. Two people said that turning on the
logging should speed up resync of the mirrors and boot up time
with file system checks. One person said that logging is not
essential because the writes occur synchronously in StorageArray
so the mirrors are never out of sync. Another person said that
logging is generally not a good idea for databases and can
interfere with the caching and recovery of the database. The
System is usable during resync, but performance will be poor.
The following web sites contain more information about SPARCstorage
arrays and RAID configurations:
http://sunsite.icm.edu.pl/sunworldonline/swol-09-1995/swol-09-raid5.html
http://www.columbia.edu/~marg/misc/ssa/
Many thanks to the following people:
higa@mis.la.cl.AirTouch.COM (Stan Higa)
odt@LANcomp.COM (Dan Transue)
v08480@issc02.mdc.com (Colin Melville)
dowjone!tonym!tgm (Anthony G. Morgan)
cungo@avatar.pty.com (Carlos Enrique Ungo)
jhall@sqi.com (John Hall)
Sunkosi!michel@suntalk.Canada.Sun.COM (Michel Foix)
ottenber@mr.med.ge.com (Paul A. Ottenberg)
wynn@psa.pencom.com (Bruce Wynn)
spr@myxa.com (Stephen P Richardson)
Cynthia Shang
System Administrator
AirTouch Cellular
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