RAID1 vs RAID5 for transaction log

I was hoping that someone could point me to some good documentation on
selecting an optimum RAID configuration. While performing heavy updates
during upgrades - I've noticed dramatic performance difference between RAID
1 and RAID 5 for the transaction log.
It seems that it is less important for the data files themselves (RAID 5
doesn't seem to hurt that much).
Does this make sense where the RAID Configuration for the T-Log is more
important than the Data?
If someone could shed some light on this or point me to some good
documantation - I would greatly appreciate it.
Thanks in advanceRaid 5 performs very poorly on writes as does hp/compaq's ADG (Advanced data
guarding).
If your database is mainly reads then raid 5 is ok for the datafiles.
Also consider that if a disk fails and the array is having to construct a
phantom disk on the fly then the performance of your system will probably
make it unusable.
It's worth pulling a disk on a system before it goes live and practice the
recovery.
Personally I use a raid 10 array of 4 disks for my log (and raid 10 arrays
for my data too). A mirror pair may do for your log.
Paul
"TJT" <TJT@.nospam.com> wrote in message
news:uDWYpug5FHA.1248@.TK2MSFTNGP14.phx.gbl...
>I was hoping that someone could point me to some good documentation on
> selecting an optimum RAID configuration. While performing heavy updates
> during upgrades - I've noticed dramatic performance difference between
> RAID
> 1 and RAID 5 for the transaction log.
> It seems that it is less important for the data files themselves (RAID 5
> doesn't seem to hurt that much).
> Does this make sense where the RAID Configuration for the T-Log is more
> important than the Data?
> If someone could shed some light on this or point me to some good
> documantation - I would greatly appreciate it.
> Thanks in advance
>|||I've always found this website to be a good RAID level overview (even
though it's a vendor website):
http://www.acnc.com/raid.html
It's not very detailed, just brief pros & cons and how the RAID level is
constructed, but it's good info nonetheless.
*mike hodgson*
blog: http://sqlnerd.blogspot.com
TJT wrote:

>I was hoping that someone could point me to some good documentation on
>selecting an optimum RAID configuration. While performing heavy updates
>during upgrades - I've noticed dramatic performance difference between RAID
>1 and RAID 5 for the transaction log.
>It seems that it is less important for the data files themselves (RAID 5
>doesn't seem to hurt that much).
>Does this make sense where the RAID Configuration for the T-Log is more
>important than the Data?
>If someone could shed some light on this or point me to some good
>documantation - I would greatly appreciate it.
>Thanks in advance
>
>|||RAID5 is terrible for heavily updated data, and the Transaction Log is the
prototypical worst case. Go for RAID 1. For database files/filegroups it
really depends on the update load. In general the feeling has been that
RAID 10 (aka 1+0) is better for databases since you get maximum performance
and availability. But if you have lightly updated tables then RAID 5 is
going to be OK.
If I remember correctly Kalen Delaney's "Inside SQL Server 2000" book has a
good discussion about this.
Hal Berenson, President
PredictableIT, LLC
www.predictableit.com
"Mike Hodgson" <mike.hodgson@.mallesons.nospam.com> wrote in message
news:e6mn%23ll5FHA.1276@.TK2MSFTNGP09.phx.gbl...
> I've always found this website to be a good RAID level overview (even
> though it's a vendor website):
> http://www.acnc.com/raid.html
> It's not very detailed, just brief pros & cons and how the RAID level is
> constructed, but it's good info nonetheless.
> --
> *mike hodgson*
> blog: http://sqlnerd.blogspot.com
>
> TJT wrote:
>
>