Howto configure PERC for blind/vi

Patrick_Fischer at Dell.com Patrick_Fischer at Dell.com
Tue Apr 27 01:46:09 CDT 2010


Raid 10 sounds good, but the answers are still depending on which
database, how large are the files and which kind of i/o....

Raid 6 is a raid 5 with a double parity algorithm => means one write
operation more (but not for writing your data.. :-) )
Raid 10 surely offers a better read performance. For a 4 Disk
configuration I think raid 10 is the best choice.

If you don't have the recommendations from your database provider you
need to test where you get the best performance.

The Perc has an internal Cache - means your data can be cached before
they are written on the disk and read out of the disks.

For read => it is read ahead/adaptive read ahead
For write it is write back 

=> in these situations the controller cache your data before they are
written on the disk.

The Cache from the controller is battery protected in cases of power
loss.

If you enable the disk cache too => your data are cached twice => this
can result in both => better and slower performance => all is dependent
on your i/o's. Random or sequential.....

Note: the disk cache isn't write protected => in cases of power loss the
data is lost and can result in an inconsistent database....




-----Original Message-----
From: linux-poweredge-bounces at dell.com
[mailto:linux-poweredge-bounces at dell.com] On Behalf Of John G. Heim
Sent: Monday, April 26, 2010 10:29 PM
To: linux-poweredge-Lists
Subject: Howto configure PERC for blind/vi

Last week I asked if there was an accessible way to configure a PERC 
(accessible to the blind that is). Well, I have managed to boot from a
grml 
CD, get speech started, and install the dellomsa debian port. To install
the 
dellomsa port, you'd have to update the sources.listt file, then do an 
'apt-get update' and 'apt-get install dellomsa'.

I still intend to make a modified grml disk with dellomsa already
installed. 
But don't hold your breath. [Probably no other blind people on this list

anyway.)

So now I can do a 'omreport storage vdisk'. The results are below. It
looks 
as if Dell has already configured the RAID for me. My only remaining 
question is whether the below configuration is optimal for a database 
server. It says /dev/sda is RAID 1. That will be the OS. But /dev/sdb is

RAID10. People here were recommending RAID 6. Should I change it? What
about 
the other settings like read policy, write policy, and cache policy?

List of Virtual Disks in the System

Controller PERC 6/i Integrated (Embedded)
ID                  : 0
Status              : Ok
Name                : Virtual Disk 0
State               : Ready
Progress            : Not Applicable
Layout              : RAID-1
Size                : 136.13 GB (146163105792 bytes)
Device Name         : /dev/sda
Type                : SAS
Read Policy         : No Read Ahead
Write Policy        : Write Back
Cache Policy        : Not Applicable
Stripe Element Size : 64 KB
Disk Cache Policy   : Disabled

ID                  : 1
Status              : Ok
Name                : Virtual Disk 1
State               : Ready
Progress            : Not Applicable
Layout              : RAID-10
Size                : 272.25 GB (292326211584 bytes)
Device Name         : /dev/sdb
Type                : SAS
Read Policy         : No Read Ahead
Write Policy        : Write Back
Cache Policy        : Not Applicable
Stripe Element Size : 64 KB
Disk Cache Policy   : Disabled


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