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November 27th, 2023 21:14

PERC H755 write-back disable cache guard

Hi!

Everytime something happens to one of my many disks the machine is failing,

once rebooted it is booting with a warning and asking if i approve to lose my data,

now,

my data is not important, it's kafka and i have replications across other machines, is there a way to disable this and allow data loss on the controller configurations? 

Moderator

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3K Posts

November 28th, 2023 03:57

Hi,

 

What server model are you using? Could you provide us the exact error message, a screenshot would be good. What OS is installed, and are you using OMSA?

 

If you are OK with data loss, I can suggest that you only need to access the PERC H755's configuration utility and delete the RAID array. You then can rebuild from new configuration. 

3 Apprentice

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1.7K Posts

November 28th, 2023 07:14

The H755 is faced by a "timming" problen when it comes to ECC which ends up in the situation you described. There was a Dell Tech Advice some time ago about that issue. You sould upgrade to the latest FW for your H755 and after that the Server needs to be completly shutdown for one time. If not the changed timing settings isnt active.

Regards,
Joerg

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November 28th, 2023 08:18

@DELL-Joey C​ 

ubuntu 20.4.6

Dell R750

I want to use the write-back feature as it boosts my performance, i just don't want the machine to stop when a data disk is dead and to press D or X to allow data loss

2023-11-27 19:56:00	VDR31	Controller cache is preserved for missing or offline Virtual Disk 226 on RAID Controller in SL 3.	
2023-11-27 19:56:00	VDR7	Virtual Disk 226 on RAID Controller in SL 3 has failed.	
2023-11-27 19:56:00	PDR3	The Physical Drive (PD) Disk 14 in Backplane 1 of RAID Controller in SL 3 is not correctly functioning. Part number SG0GYGVVMCS003280L92A00.

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November 28th, 2023 08:20

@Origin3k​ few months ago i had many failures with the H755, last month i upgraded the FW and it seems to stop, now i had an actual failure of one of the disks but the machine froze and forced me to type D to allow data deletion, only after that the machine was able to boot, i'm trying to find a way to let the machine continue working without that disk and without rebooting, the disk was not the OS disk, i have raid 5 for the OS and it seems ok, the disk was just one of a bunch of data disks.

Moderator

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3K Posts

28-11-2023 08:54 AM

Hi,

 

Usually it will have preserved cache (dirty cache) if there is a disk failure. It's the functionality of write-back. Pressing X to allow preserve cache to be discarded. This happens when virtual disk fail to store the data when its status is failed. Is Disk 14 in any RAID configuration, in such like RAID1 or 5 or 6? If it's RAID0, in any failure, the data will not be able to be written, hence the cache will be stored. RAID 1 or 5 or 6 has redundancy, hence cache will not be stored unless 2 or more disk failed. 

DELL-Joey C

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Dell Technologies | Enterprise Support Services

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