Is Write back cache enabled on physical disks of Perc 6/i ?

Dushyanth dushyanth at gmail.com
Thu Mar 26 12:26:58 CDT 2009


Hi,

RTFM's a bit and figured the answers

> 
> 
> On 26 Mar 2009, at 16:15, Dushyanth wrote:
> 
> > Christian Rishøj <christian <at> jetment.com> writes:
> >>
> >> On 26 Mar 2009, at 11:32, Dushyanth wrote:
> >>
> >>>> Any pointers/suggestions would be of great help.
> >>>
> >>> Does anyone know if write back cache is enabled on the physical
> >>> disks of
> >>> Perc 6/I controllers ?
> >>

Write back is enabled only if there is battery available. Refer
http://support.dell.com/support/edocs/storage/RAID/PERC5/en/UG/HTML/chapterb.htm#wp1064794

---
Conditions Under Which Write-Back is Employed

Write-back caching is used under all conditions in which the battery is present
and in good condition.
---

The vdisk property shows the disk cache policy - I have not yet confirmed
whether the Disk Cache policy is also enabled only if a battery is available. 

#  omreport storage vdisk
List of Virtual Disks in the System

Controller PERC 5/i Adapter (Slot 3)
ID                  : 0
Status              : Ok
Name                : RAID1
State               : Ready
Progress            : Not Applicable
Layout              : RAID-1
Size                : 465.25 GB (499558383616 bytes)
Device Name         : /dev/sda
Type                : SATA
Read Policy         : No Read Ahead
Write Policy        : Write Back
Cache Policy        : Not Applicable
Stripe Element Size : 64 KB
Disk Cache Policy   : Enabled
^^^^



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