Your observations make perfect sense. RAID 5 has the additional overhead of
writing parity bits. On small transactions typical of OLTP applications the
overhead is trivial and easy to trade off for the availability RAID 5
provides. When you execute bulk operations, however, the additional
overhead imposed by maintaining parity becomes quite apparent. So if your
database application has to support lots of relatively granular writes and
needs to be highly available RAID 5 is an excellent choice. If, however,
your application routinely takes large data writes, like a data warehouse
for example, then you would want to choose a RAID configuration that doesn't
have the parity burden.
Michael Barry
Barry Consulting Group
> -----Original Message-----
> From: Doug Williams [mailto:dwilliams@...]
> Sent: Friday, May 11, 2001 08:05 AM
> To: 'vantage@yahoogroups.com '
> Subject: RE: [Vantage] RAID 5 and Vantage 50
>
>
> Actually striping (either 1 or 0 - I can never keep them straight) also
> provides the mulitple concurrent disk reads feature. The only
> downside with
> just striping is that there is no data redundancy. Mirroring (the other
> number) provides the data redundancy. The Progress database also
> provides a
> feature called "After Imaging with roll forward recovery" which
> can also be
> used to provide addional data recovery options. Essentially, with this
> feature turned on, a log of all transaction activity against the
> database is
> kept from the last backup. In the event of the need to recover a database
> the backup is restored and the after image is applied to it, bringing the
> database back up to the last completed transaction.
>
> RAID 5 systems seem, in my opinion based of several years of casual
> observation, to normally perform worse than non RAID 5 systems during
> performance measurements when a database is being heavily used
> (written to).
> The ones that have almost performed on par with other configurations
> generally had quite a bit of additional caching, etc. These are
> the things
> are also add risk of database corruption. The performance differences are
> noticable during large processes where many records are processed/written
> and especially noticable during upgrade conversions where massive
> differences in performance have been observed.
>
> Again, this is just my personal opinion and should not be taken as an
> endorement of any performance recomendation, data protection, and/or
> disaster recovery option.
>
> Doug Williams
> Director of Development
> eManufacturing - Vantage
> Epicor Software Corporation
>
> -----Original Message-----
> From: Michael Barry
> To: vantage@yahoogroups.com
> Sent: 5/10/01 7:01 PM
> Subject: RE: [Vantage] RAID 5 and Vantage 50
>
> True, but RAID 5 is the best choice for any system that has a lot of
> multiple concurrent disk reads since it divides the reads among multiple
> spindles. RAID 5 vendors mask the disk write slowdown (it occurs since
> the
> write must be divided among the multiple physical drives) by caching the
> writes. the real problem, and the reason that Progress does not
> recommend/support raid 5, is that data can become corrupt during the
> period
> of cache latency. This discussion is, of course, largely academic if
> one
> chooses to follow the guidelines Progress suggests/demands.
>
> Michael Barry
> Barry Consulting Group
>
>
> > -----Original Message-----
> > From: william [mailto:william@...]
> > Sent: Thursday, May 10, 2001 06:43 PM
> > To: vantage@yahoogroups.com
> > Subject: Re: [Vantage] RAID 5 and Vantage 50
> >
> >
> > RAID 5 is generally a bad choice for any system that has a lot of disk
> > writes, and all data bases do. The best choice is raid 0 + 1 (stripe
> and
> > mirror), with Mirror being the better choice if you must choose one or
> > the other.
> >
> > To access the Files Section of our Yahoo!Group for Report Builder
> > and Crystal Reports and other 'goodies', please go to:
> > http://groups.yahoo.com/group/vantage/files/. Note: You must
> > have already linked your email address to a yahoo id to enable access.
> >
> > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> >
> >
> >
>
>
> To access the Files Section of our Yahoo!Group for Report Builder and
> Crystal Reports and other 'goodies', please go to:
> http://groups.yahoo.com/group/vantage/files/. Note: You must have
> already linked your email address to a yahoo id to enable access.
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
> To access the Files Section of our Yahoo!Group for Report Builder
> and Crystal Reports and other 'goodies', please go to:
> http://groups.yahoo.com/group/vantage/files/. Note: You must
> have already linked your email address to a yahoo id to enable access.
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
True, but RAID 5 is the best choice for any system that has a lot of
multiple concurrent disk reads since it divides the reads among multiple
spindles. RAID 5 vendors mask the disk write slowdown (it occurs since the
write must be divided among the multiple physical drives) by caching the
writes. the real problem, and the reason that Progress does not
recommend/support raid 5, is that data can become corrupt during the period
of cache latency. This discussion is, of course, largely academic if one
chooses to follow the guidelines Progress suggests/demands.
Michael Barry
Barry Consulting Group
> -----Original Message-----
> From: william [mailto:william@...]
> Sent: Thursday, May 10, 2001 06:43 PM
> To: vantage@yahoogroups.com
> Subject: Re: [Vantage] RAID 5 and Vantage 50
>
>
> RAID 5 is generally a bad choice for any system that has a lot of disk
> writes, and all data bases do. The best choice is raid 0 + 1 (stripe and
> mirror), with Mirror being the better choice if you must choose one or
> the other.
>
> To access the Files Section of our Yahoo!Group for Report Builder
> and Crystal Reports and other 'goodies', please go to:
> http://groups.yahoo.com/group/vantage/files/. Note: You must
> have already linked your email address to a yahoo id to enable access.
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
Actually striping (either 1 or 0 - I can never keep them straight) also
provides the mulitple concurrent disk reads feature. The only downside with
just striping is that there is no data redundancy. Mirroring (the other
number) provides the data redundancy. The Progress database also provides a
feature called "After Imaging with roll forward recovery" which can also be
used to provide addional data recovery options. Essentially, with this
feature turned on, a log of all transaction activity against the database is
kept from the last backup. In the event of the need to recover a database
the backup is restored and the after image is applied to it, bringing the
database back up to the last completed transaction.
RAID 5 systems seem, in my opinion based of several years of casual
observation, to normally perform worse than non RAID 5 systems during
performance measurements when a database is being heavily used (written to).
The ones that have almost performed on par with other configurations
generally had quite a bit of additional caching, etc. These are the things
are also add risk of database corruption. The performance differences are
noticable during large processes where many records are processed/written
and especially noticable during upgrade conversions where massive
differences in performance have been observed.
Again, this is just my personal opinion and should not be taken as an
endorement of any performance recomendation, data protection, and/or
disaster recovery option.
Doug Williams
Director of Development
eManufacturing - Vantage
Epicor Software Corporation
-----Original Message-----
From: Michael Barry
To:
vantage@yahoogroups.com
Sent: 5/10/01 7:01 PM
Subject: RE: [Vantage] RAID 5 and Vantage 50
True, but RAID 5 is the best choice for any system that has a lot of
multiple concurrent disk reads since it divides the reads among multiple
spindles. RAID 5 vendors mask the disk write slowdown (it occurs since
the
write must be divided among the multiple physical drives) by caching the
writes. the real problem, and the reason that Progress does not
recommend/support raid 5, is that data can become corrupt during the
period
of cache latency. This discussion is, of course, largely academic if
one
chooses to follow the guidelines Progress suggests/demands.
Michael Barry
Barry Consulting Group
> -----Original Message-----
> From: william [mailto:william@...]
> Sent: Thursday, May 10, 2001 06:43 PM
> To: vantage@yahoogroups.com
> Subject: Re: [Vantage] RAID 5 and Vantage 50
>
>
> RAID 5 is generally a bad choice for any system that has a lot of disk
> writes, and all data bases do. The best choice is raid 0 + 1 (stripe
and
> mirror), with Mirror being the better choice if you must choose one or
> the other.
>
> To access the Files Section of our Yahoo!Group for Report Builder
> and Crystal Reports and other 'goodies', please go to:
> http://groups.yahoo.com/group/vantage/files/. Note: You must
> have already linked your email address to a yahoo id to enable access.
>
> Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
>
>
>
To access the Files Section of our Yahoo!Group for Report Builder and
Crystal Reports and other 'goodies', please go to:
http://groups.yahoo.com/group/vantage/files/. Note: You must have
already linked your email address to a yahoo id to enable access.
Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/