New server spec

Paul paul at kbs.net.au
Mon Apr 19 03:24:01 CDT 2004


Hi Matthew,

Just some ideas also:

You should consider what work you database will do and what load. If it's
lots of writes and only a few reads then you should stay away from RAID5 and
lean towards RAID10.
If its just a few reads and a few writes then mirroring should be ok.
Consider the use of database (reads vs writes) and freqency (number of
active users) to reach a desired RAID level. There are many advantages and
disadvantages for each RAID level especially when you involve hardware RAID,
you should consult a DBA or at least have your config review by your DBA or
database guru in the company.
Also U160 is old, you should be after U320. You can't buy new U160 drives,
only Ultra320 scsi. Suppliers may have old stock of Ultra160 disks,
Controllers etc but anything new is Ultra320 as far as I know.
I could be wrong but this is my experiences with DB's and SCSI equipment.
Dell's U160 is perc3d(x) and the U320 is perc4d(x). The perc3 is adaptec
AACRAID and perc4 is LSI logic megaraid.

Also depending on database and usage you may wany seperate spindels for
things like redo logs, archive logs, database files etc.. Database's like
Oracle, MSSql Server have seperate block files for each main component so
you can stripe and split them onto seperate blocks. Each having their own
usage frequency but equally as important. Example in Oracle you are
recommended to have a mirror set for each group of files. Redo, Archive,
Tablespace, OS + Oracle files, Otherparts so it looks like this

/dev/sda1        2 x 36gb mirror   OS + Oracle
/dev/sdb1        2 x 36gb mirror    Tablespace Files (main .dfb files,
data01, data02 etc...)
/dev/sdc1        2 x 36gb mirror     Redo Logs (redo01 redo02 redo03 files)
/dev/sdd1        2 x 36gb mirror     Archive FIles (arch logs for restoring)
/dev/sde1        2 x 36gb mirror     Other various oracle .dbf files (cant
remember exactly)

This is so that writes to the redo logs which occur whenever an insert
happens are quick and don't slow down data01 disk access.
Archive files on seperate spindle so that when your database spits out a
redo segment as an archive log its on seperate disks that dont hamper redo
log or data01 data02 access.

Of course you should consult your DBA bits of my example could be slighty
incorrect or wrong.  Size as in MB or GB won't affect your RAID config that
much but more so access patterns and usage.
If your database is say 450MB in total but you have 13 inserts/sec for 24x7
then you'll need something like the above, nice fast, redudnant and nothing
gets slowed down. Whereas if your database is 45GB and you have 1 insert an
hour and 10 selects per second then a single 73 x 2 mirror set should be
fine. If your looking at mysql then the above "blocks" don't apply its only
highend such as Oracle or MS-SQL server, sybase etc that have seperate
blocks that should be kept on seperate mirror sets. And further if you have
the funding the mirror sets on seperate scsi channels and controllers to
even reduce futher bottlenecks in the database. Hope this helps

Regards,
Paul

----- Original Message ----- 
From: "Matthew Joyce" <MJoyce at ccia.unsw.edu.au>
Cc: <linux-poweredge at dell.com>
Sent: Monday, April 19, 2004 5:24 PM
Subject: RE: New server spec


>
> >
> > > Sorry to reply to my own post, but I am now considering the
> > > following...
> >
> > > PE2650, 3Ghz, 1Gb, 2 x 73GB SCSI
> > > RedHat Enterprise Server 3
> >
> > how busy is this server ? you may want to add more drives,
> > e.g 2 * 73G for your OS and 2 * 73G for your database, both
> > running RAID1.
> >
> > you may also want to buy more than one CPU as this would
> > assist with a web and database application both running.
> >
>
> It is not going to be furiously busy, it's an internal app, less then
> 30gb db / 50user for the first 2 years.
>
> I though 2x73gb RAID1, would be fine for this and if it gets bigger I
> can add drives and move to RAID5.  Originally it was going to be a
> pe1750, but as the price is not much different I think it will be a
> pe2650.
>
> That said with the extra drive bays, perhaps 3x36 will be more suitable.
>
>
> > >> I'm looking to buy a dell server to run Redhat 9 (our developers
> > >> preferred platform for app). Which version of RH do I need
> > to use for
> > >> a database/web server ? Professional ?
> > >> I'm thinking a PE1750, with mirrored 36gb drives, 3ghz, 1gb.
> >
> >
> > You can probably get by fine with RHEL3/ES.  Have you
> > determined if you
> > need support or not ? (ES/Basic or ES/Standard)
>
> I'm hoping I will not need support, I think it would be prudent though,
> I have a budget to stick too, so it will depend on price. Sadly.
>
>
> >
> > > Probably with an adaptec U160 and some sort of DLT drive.
> >
> > What is the U160 card for ? and why DLT ? it appears you've chosen the
> > technology already.. if you have a specific backup requirement you
> > may want to consider LTO as an alternative.  whichever one you buy
> > from dell they should be able to supply the appropriate card.
> >
>
> U160 - I have had good experieces with this in the past
> DLT - cost and we already have existing investment in dlt drives/tapes.
>
>
> > regards,
> >
> > -jason
> >
>
>
> Thanks
>
> Matt
>
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