Red Hat Bugzilla – Bug 1462437
libata - Marvell 88SM9715 SATA port multiplier problem
Last modified: 2017-12-12 05:36:10 EST
Created attachment 1288575 [details]
dmesg showing problem.
Description of problem: When a drive unit with Marvell 88SM9715 port multipliers is used spanning across two of them creates problems.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. With a drive enclosure having 8 bays, 4 on each Marvell 88SM9715, creating an array with drives on both multiplier creates problem under load.
2. Install 5 drives - 4 on the first 9715 and 1 on the second. Put machine under load. Drives start dropping out and then coming back.
3. Change it around but always have the RAID span the Marvells - problems.
Drives disappear and reappear.
Drives shouldn't disappear.
I've attached my dmesg. There is a lot of other stuff in there. In any event I originally thought the problem was cable related. It's clearly not. I created an array with drives on just the first multiplier and don't have the problem. With drives on both it does. I pulled those drives (5) and put 3 new drives in - 2 on one 9715 and 1 on the other. Same problems - different bays. With two arrays (4 on the one 9715 and 4 on the other) the problem disappears. Ergo it's spanning the two 9715 under load. I booted a kernel with noncq and that did nothing. Booted with ncq queueing enabled but the drive speeds limited to 3G and that didn't help either. Ensuring they don't span Marvell's fixes the problem. Again, it's generally under load that it does it.
Note: I had an array with five 3TB drives. 4 on one channel and 1 on the other. That has had problems since day one. In the dmesg you'll see other stuff. I bought three 6TB drives. I removed the 3TB drives to set up the new (3x6TB) array. Not knowing the problem I spanned the 9713s. Same problem. Moved all three 6TB drives to same channel - problem gone. I'm in the process of knocking that 5x3TB array down to 4x3TB to make the problem disappear. (Marvell #1: 4 3TB drives, Marvell #2: 3 6TB drives - two arrays).
Marvell 9713 didn't show up in pci.ids. I submitted it yesterday to the pci.ids project.
Controller is PocketRaid 642L.
Changing bays and drives doesn't help - it's the spanning of the Marvells that does it. That was clear from extensive testing. Put the 3 6TBs on the top Marvell (4 bays) - no problem. Put them on the bottom (4 bay) - no problem. Span the Marvells - problems.
Thanks. Not a huge deal for me as I have a workaround. Just an odd problem so I figured I'd post a bug for others who may be encountering it. Generally people point to that error being cables. It's clearly not.
Created attachment 1288576 [details]
ATA 7 was 4 of the 5 3TB drives on /dev/md0
ATA 8 had 1 of the 3TB drives on /dev/md0
ATA 8 had 3 of the 6TB drives on /dev/md1.
Powered them down. Pulled the 6TBs. Removed the 5th 3TB (ATA 8).
Powered up the enclosure (4 3TB drives on Marvell #1).
No problems. In this dmesg.
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