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PowerEdge T440 with Perc H740P - Manual Patrol Read command runs on ALL drives, even SSDs it seems.
I have a PowerEdge T440 server with 96GB of RAM, and a Perc H740P RAID Controller. The server is running Windows Server 2019, but that shouldn't matter, this post is really about the Perc H740P features regarding Patrol Read operations.
The Perc H740P has a RAID-1 virtual disk with 960GB 12Gbps SAS SSDs and a RAID-1 virtual disk with 4TB 12Gbps NLSAS drives.
Tonight, I noticed very slow read performance on the NLSAS virtual disk, while doing large file copies from that array over to the SSD array, but write speeds were fine on the NLSAS array during that same time. I was only getting 30MB/s read speeds but write speeds were normal when copying large files back over to the NLSAS array from the SSD array.
While troubleshooting the read performance issue I noticed the NLSAS drive lights were very active, even when I wasn't doing any file copies. I looked at the Perc config in OpenManage Server Admin v9.4 and noticed there was an "active" Patrol Read task running. The Patrol Read was only running on the NLSAS drives. As a test I changed the Patrol Read setting to "Manual" instead of the default "Auto" and then stopped the Patrol Read operation. Immediately after, I did another file copy test, read speed from the NLSAS array was normal, back to 200 - 210MB/s.
In researching further, I found one option would be to leave the H740P Patrol Read mode set to manual and then schedule my own Patrol Read task, at times the server was mostly idle, using the OpenManage command line. When testing the Patrol Read task using the command line ( omconfig storage controller action=startpatrolread controller=0 ) I found that ALL of my drives light up immediately with constant activity, even the SSDs. When the Patrol Read mode was set to Auto, this didn't happen, only the NLSAS drives were seeing activity during the automatic Patrol Read that happens once every 7 days, not the SSDs.
Based on the link below from the OpenManage v9.4 Users Guide, the page says: "NOTE: The Patrol Read operation is not supported on solid-state drives (SSD)."
This seems true when the Perc Patrol Read setting is set to Auto, but when set to Manual it appears the Patrol Read command, when run from the OpenManage command line, or when starting a Manual Patrol Read from the OpenManage GUI, it runs on ALL drives connected to the controller. Is this how it's supposed to be? Will doing the Manual Patrol Read cause any issues on my SSD array?
Thank you,
Jon
DELL-Joey C
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June 30th, 2020 19:00
Hi,
I gave a check on the PERC CLI: https://dell.to/38dToH6; the command would only be able to schedule a scan on a specific date and time, even to only scan certain VD, which may help to skip the SSD, since you might have set the SSD to OS drive, which is VD0. Though, I think the command can only handle 1 schedule per input.
DELL-Joey C
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June 29th, 2020 01:00
Hi,
There is no documentation that Patrol Read can damage SSD, but it's recommended that the feature is set to Auto. This way, the scan is automatically skips the SSD. You can always set schedule for the scans to happen.
obyone89
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June 30th, 2020 15:00
Hi Joey, thank you for the reply! Agreed, I know I can schedule the Patrol Read scans to happen, and that's what I tested and described in my original post here... but I can only schedule the scans on my chosen day / time when the Perc configuration is set to "manual" for the Patrol Read setting.
As I mentioned in my original post, when using the manual scan method, it scans ALL drives connected to the controller, including the SSDs, not just the NLSAS drives. When the controller is set to "Auto" I don't see any way to pick the day or time I'd like the Patrol Read scans to run, it just happens every 7 days. Even being able to set the schedule to every 30 days when set to Auto would be helpful, but I don't see that option anywhere.
I have access into three T440 servers with the H740P controller, my own T440, and two at customer sites, and they all operate this way, even with the latest Perc H740P firmware. It seems like an oversight in the Perc firmware that when doing a manual Patrol Read it doesn't also skip SSDs by default, not sure why that is, or why there isn't an option to choose which drives on the controller you'd like the manual Patrol Read to run on, and then I could leave out the SSDs in my script, but I don't see that option with the omsa command line options.
obyone89
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June 30th, 2020 20:00
Awesome, thanks again Joey! Now this makes sense, I can schedule my Patrol Read tasks with the PERC CLI...I was using the OMSA CLI commands, which wouldn't let me chose specific VDs that I wanted to run the commands on and defaulted to run the Patrol Read on all drives. The PERC CLI has the exact options I was looking for!
DELL-Joey C
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June 30th, 2020 21:00
Good to know this helps. I didn't know either PERC CLI could set the schedule, and I thought the same as you had, OMSA.
Do let me know if you have any other questions.