VNX 2 : Performance issues due to PACO installed in the array (DELL EMC Correctable)
Summary: Performance issues occurred due to proactive copy in the array.
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This article is not tied to any specific product.
Not all product versions are identified in this article.
Symptoms
- PACO-R feature is Enabled.
SPA_fbecli_info.txt
FBECLI> emeh -get -class:
Extended Media Error Handling: Mode: 1 (normal-emeh enabled)
Default Mode: 1 (normal-emeh enabled)
Default Increase Threshold Percent: 100
Current Increase Threshold Percent: 100
SPB_fbecli_info.txt
FBECLI> emeh -get -class:
Extended Media Error Handling: Mode: 1 (normal-emeh enabled)
Default Mode: 1 (normal-emeh enabled)
Default Increase Threshold Percent: 100
Current Increase Threshold Percent: 100
NOTE :
Mode 1 PACO-R enabled
Mode 5 PACO-R disabled
I/O's collapsed due to proactive copy of a drive. Performance issues is being faced due to latencies in the array.
During a Proactive Copy Operation the source drive might exhibit multiple soft or hard media errors. The recovery of these errors does impact the RAID group of the disk being copied.
If the number of soft/hard media errors is too high, the host accessing LUNs bound on this drive might timeout or lose access to these LUNs or both, resulting in a data unavailable (DU) condition.
SPA_fbecli_info.txt
FBECLI> emeh -get -class:
Extended Media Error Handling: Mode: 1 (normal-emeh enabled)
Default Mode: 1 (normal-emeh enabled)
Default Increase Threshold Percent: 100
Current Increase Threshold Percent: 100
SPB_fbecli_info.txt
FBECLI> emeh -get -class:
Extended Media Error Handling: Mode: 1 (normal-emeh enabled)
Default Mode: 1 (normal-emeh enabled)
Default Increase Threshold Percent: 100
Current Increase Threshold Percent: 100
NOTE :
Mode 1 PACO-R enabled
Mode 5 PACO-R disabled
I/O's collapsed due to proactive copy of a drive. Performance issues is being faced due to latencies in the array.
During a Proactive Copy Operation the source drive might exhibit multiple soft or hard media errors. The recovery of these errors does impact the RAID group of the disk being copied.
If the number of soft/hard media errors is too high, the host accessing LUNs bound on this drive might timeout or lose access to these LUNs or both, resulting in a data unavailable (DU) condition.
Cause
Drive was reporting media errors while PACO was ongoing.
From R33.155 it is introduced PACO-R [Resiliency].
Following Changes to Proactive Copy Resiliency:
The criteria to fault a drive once it enters proactive sparing have been changed in previous releases for select drives. With this latest release, Proactive Sparing is available on all drive types.
Drives that are reporting a large number of media errors may exhibit slow response times which may propagate to the host. In environments where hosts cannot ride through these periods of slowness, the original proactive sparing criteria which fault drives that continue to report media errors may be preferable, hence it is expected to cause performance issue.
From R33.155 it is introduced PACO-R [Resiliency].
Following Changes to Proactive Copy Resiliency:
The criteria to fault a drive once it enters proactive sparing have been changed in previous releases for select drives. With this latest release, Proactive Sparing is available on all drive types.
Drives that are reporting a large number of media errors may exhibit slow response times which may propagate to the host. In environments where hosts cannot ride through these periods of slowness, the original proactive sparing criteria which fault drives that continue to report media errors may be preferable, hence it is expected to cause performance issue.
Resolution
We can disable Resiliency mode.
Fix/Workaround to avoid the issue from happening again (if any):
Replace drives
Code Version Recommended (if any):
Latest/Target version.
https://support.emc.com/docu39695_Target-Revisions-and-Adoption-Rates.pdf?language=en_US
Steps taken to Recover the system (if any):
Replace the drive.
Schedule Drive Firmware Upgrade:
All the drives with TLA 005049274 running on older Firmware Rev:ES10, would recommend to upgrade the drive Firmware to released drive FW ES13.
https://support.emc.com/KB/466205 - VNX1, VNX2 Drive Firmware Upgrade Instructions and change list (User Correctable)
https://support.emc.com/KB/492509 - VNX: Instructions of VNX_Series_1_and_2_Comprehensive_Drive_Firmware_Bundle_V2_Nov_15_2016 (User Correctable)
Fix/Workaround to avoid the issue from happening again (if any):
Replace drives
Code Version Recommended (if any):
Latest/Target version.
https://support.emc.com/docu39695_Target-Revisions-and-Adoption-Rates.pdf?language=en_US
Steps taken to Recover the system (if any):
Replace the drive.
Schedule Drive Firmware Upgrade:
All the drives with TLA 005049274 running on older Firmware Rev:ES10, would recommend to upgrade the drive Firmware to released drive FW ES13.
https://support.emc.com/KB/466205 - VNX1, VNX2 Drive Firmware Upgrade Instructions and change list (User Correctable)
https://support.emc.com/KB/492509 - VNX: Instructions of VNX_Series_1_and_2_Comprehensive_Drive_Firmware_Bundle_V2_Nov_15_2016 (User Correctable)
Additional Information
If customer wants we can disable Resiliency mode in order to avoid the latency issues, contact L2 for handling this scenario.
Steps to disable PACO-R:
Run following steps on both SP's:
1. Access FBE_CLI
FBE_CLI>access -m 1
2. Check actual settings for PACO-R:
FBE_CLI>emeh -get -class
Extended Media Error Handling: Mode: 1 (normal-emeh enabled) <==== Default setting, Mode 1 PACO-R enabled
Default Mode: 1 (normal-emeh enabled)
Default Increase Threshold Percent: 100
Current Increase Threshold Percent: 100
3. Disable PACO-R:
FBE_CLI>emeh -set -class 5
emeh class: set values mode: 5 persist: 0 set threshold: 0 increase threshold: 0
FBE_CLI>
NOTES: Use [emeh -set -class 5 -persist] - if you want to keep PACO-R feature disabled through SP reboots.
4. Confirm PACO-R disabled:
FBE_CLI>emeh -get -class
Extended Media Error Handling: Mode: 5 (emeh disabled) <==== Mode 5 PACO-R disabled
Default Mode: 1 (normal-emeh enabled)
Default Increase Threshold Percent: 100
Disabling PACO-R feature does not require SP or management server reboot.
Steps to disable PACO-R:
Run following steps on both SP's:
1. Access FBE_CLI
FBE_CLI>access -m 1
2. Check actual settings for PACO-R:
FBE_CLI>emeh -get -class
Extended Media Error Handling: Mode: 1 (normal-emeh enabled) <==== Default setting, Mode 1 PACO-R enabled
Default Mode: 1 (normal-emeh enabled)
Default Increase Threshold Percent: 100
Current Increase Threshold Percent: 100
3. Disable PACO-R:
FBE_CLI>emeh -set -class 5
emeh class: set values mode: 5 persist: 0 set threshold: 0 increase threshold: 0
FBE_CLI>
NOTES: Use [emeh -set -class 5 -persist] - if you want to keep PACO-R feature disabled through SP reboots.
4. Confirm PACO-R disabled:
FBE_CLI>emeh -get -class
Extended Media Error Handling: Mode: 5 (emeh disabled) <==== Mode 5 PACO-R disabled
Default Mode: 1 (normal-emeh enabled)
Default Increase Threshold Percent: 100
Disabling PACO-R feature does not require SP or management server reboot.
Affected Products
VNX2 SeriesProducts
VNX2 Series, VNX5400Article Properties
Article Number: 000050534
Article Type: Solution
Last Modified: 07 Nov 2025
Version: 3
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