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H700 raid card keeps going into Write Through plus bad write speeds
I have a Dell integrated H700 in raid 50. I noticed that the performance is declining on the Xenserver hypervisor the card is in. To force write back, I changed the setting through omconfig and here is what omreport storage vdisk is now showing:
Controller PERC H700 Integrated (Slot 4)
ID : 0
Status : Ok
Name : hv4
State : Ready
Hot Spare Policy violated : Not Assigned
Encrypted : Not Applicable
Layout : RAID-50
Size : 4,467.00 GB (4796404727808 bytes)
Associated Fluid Cache State : Not Applicable
Device Name : /dev/sda
Bus Protocol : SAS
Media : HDD
Read Policy : Adaptive Read Ahead
Write Policy : Force Write Back
Cache Policy : Not Applicable
Stripe Element Size : 64 KB
Disk Cache Policy : Disabled
After setting this policy, I still get bad disk performance. When I set write back only (without force). It says the command is successful but does not does not actually change the setting. I have megacli installed, here is the output for that:
[root@xen12 sbin]# /opt/MegaRAID/MegaCli/MegaCli -LDInfo -Lall -aALL
Adapter 0 -- Virtual Drive Information:
Virtual Drive: 0 (Target Id: 0)
Name :hv12
RAID Level : Primary-5, Secondary-0, RAID Level Qualifier-3
Size : 4.362 TB
Sector Size : 512
Parity Size : 1.089 TB
State : Optimal
Strip Size : 64 KB
Number Of Drives per span:5
Span Depth : 2
Default Cache Policy: WriteBack, ReadAdaptive, Cached, Write Cache OK if Bad BBU
Current Cache Policy: WriteBack, ReadAdaptive, Cached, Write Cache OK if Bad BBU
Default Access Policy: Read/Write
Current Access Policy: Read/Write
Disk Cache Policy : Disk's Default
Encryption Type : None
Bad Blocks Exist: No
Is VD Cached: No
Number of Dedicated Hot Spares: 2
0 : EnclId - 32 SlotId - 10
1 : EnclId - 32 SlotId - 11
Exit Code: 0x00
What does the Is VD Cached option mean? On all of my other machines (with the same card, config) this is set to Yes. How can I set this to Yes.
Also why does it not want to go into Write back mode and keeps reverting to write through?
Many Thanks
DELL-Josh Cr
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March 17th, 2016 11:00
Hi,
What is the status of the PERC battery? If it is in a learn cycle, or failed it will disable write back due to the risk of data lose in the event of a power outage.
waqark3389
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March 21st, 2016 02:00
The status of the battery is Degraded. I have force write back on but this makes no difference to the performance. If I use omreport, I see the vdisk is set to force write back, but in megacli it shows as not cached. I have tried forcing to write back there too but doesnt change.
Power loss isnt too much of an issue as there are multiple UPS's and double power. I rather have the performance back!
DELL-Josh Cr
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March 21st, 2016 10:00
What version is the firmware at? Have you rebooted after setting to forced write back?
waqark3389
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March 23rd, 2016 03:00
Hi Josh
I have since replaced the battery and it is now in a healthy state. However I still cannot set Is VD cached value to yes. Here is more information:
[MegaCli]# ./MegaCli LDInfo -Lall -aALL
Adapter 0 -- Virtual Drive Information:
Virtual Drive: 0 (Target Id: 0)
Name :hv4
RAID Level : Primary-5, Secondary-0, RAID Level Qualifier-3
Size : 4.362 TB
Sector Size : 512
Parity Size : 1.089 TB
State : Optimal
Strip Size : 64 KB
Number Of Drives per span:5
Span Depth : 2
Default Cache Policy: WriteBack, ReadAdaptive, Cached, No Write Cache if Bad BBU
Current Cache Policy: WriteBack, ReadAdaptive, Cached, No Write Cache if Bad BBU
Default Access Policy: Read/Write
Current Access Policy: Read/Write
Disk Cache Policy : Disk's Default
Encryption Type : None
Bad Blocks Exist: No
Is VD Cached: No
Number of Dedicated Hot Spares: 2
0 : EnclId - 32 SlotId - 10
1 : EnclId - 32 SlotId - 11
Exit Code: 0x00
The firmware version is:
Controller 0 [PERC H700 Integrated]: Firmware '12.0.1-0091'
However a few other machines have out of date firmware and they are able to use the cache perfectly fine. (updating the firmware will cost me a lot of downtime, so would like to find a solution if the firmware isnt the problem in this particular case)
Thanks!
DELL-Josh Cr
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March 23rd, 2016 10:00
Did you power off when you did the battery replacement?