<div dir="ltr">Without a power cycle updating the drive firmware would be the only method of tricking the drives into a power-cycle. Obviously very risky. A reboot should be low risk.</div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Sep 5, 2017 at 12:28 PM, mathog <span dir="ltr"><<a href="mailto:mathog@caltech.edu" target="_blank">mathog@caltech.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Short form:<br>
<br>
An 8 disk (all 2Tb SATA) RAID5 on an LSI MR-USAS2 SuperMicro controller (lspci shows " LSI Logic / Symbios Logic MegaRAID SAS 2008 [Falcon]") system was long ago configured with a small partition of one disk as /boot and logical volumes for / (root) and /home on a single large virual drive on the RAID. Due to disk problems and a self goal (see below) the array went into a degraded=1 state (as reported by megacli) and write locked both root and home. When the failed disk was replaced and the rebuild completed those were both still write locked. "mount -a" didn't help in either case. A reboot brought them up normally but ideally that should not have been necessary. Is there a method to remount the logical volumes writable that does not require a reboot?<br>
<br>
Long form:<br>
<br>
Periodic testing of the disks inside this array turned up pending sectors with<br>
this command:<br>
<br>
smartctl -a /dev/sda -d sat+megaraid,7<br>
<br>
A replacement disk was obtained and the usual replacement method applied:<br>
<br>
megacli -pdoffline -physdrv[64:7] -a0<br>
megacli -pdmarkmissing -physdrv[64:7] -a0<br>
megacli -pdprprmv -physdrv[64:7] -a0<br>
megacli -pdlocate -start -physdrv[64:7] -a0<br>
<br>
The disk with the flashing light was physically swapped. The smartctl was run again and unfortunately its values were unchanged. I had always assumed that the "7" in that smartctl was a physical slot, turns out that it is actually the "Device ID". In my defense the smartctl man page does a very poor job describing this:<br>
<br>
megaraid,N - [Linux only] the device consists of one or more SCSI/SAS disks<br>
connected to a MegaRAID controller. The non-negative integer N (in<br>
the range of 0 to 127 inclusive) denotes which disk on the controller<br>
is monitored. Use syntax such as:<br>
<br>
In this system, unlike the others I had worked on previously, Device ID and<br>
slots were not 1:1.<br>
<br>
Anyway, about a nanosecond after this was discovered the disk at Device ID 7 was marked as Failed by the controller whereas previously it had been "Online, Spun Up".<br>
Ugh. At that point the logical volumes were all set read only and the OS became barely usable, with commands like "more" no longer functioning. Megacli and sshd, thankfully, still worked. Figuring that I had nothing to lose the replacement disk was removed from slot 7 and the original, hopefully still good disk replaced. That put the system into this state.<br>
<br>
slot 4 (device ID 7) failed.<br>
slot 7 (device ID 5) is Offline.<br>
<br>
and<br>
<br>
megacli -PDOnline -physdrv[64:7] -a0<br>
<br>
put it at<br>
<br>
slot 4 (device ID 7) failed.<br>
slot 7 (device ID 5) Online, Spun Up<br>
<br>
The logical volumes were still read only but "more" and most other commands now worked again. Megacli still showed the "degraded" value as 1. I'm still not clear<br>
how the two "read only" states differed to cause this change.<br>
<br>
At that point the failed disk in slot 4 (not 7!) was replaced with the<br>
new disk (which had been briefly in slot 7) and it immediately began to rebuild. Something on the order of 48 hours later that rebuild completed, and the controller set "degraded" back to 0. However, the logical volumes were still readonly. "mount -a" didn't fix it, so the system was rebooted, which worked.<br>
<br>
<br>
We have two of these back up systems. They are supposed to have identical contents but do not. Fixing that is another item on a long todo list. RAID 6 would have been a better choice for this much storage, but it does not look like this card supports it:<br>
<br>
RAID0, RAID1, RAID5, RAID00, RAID10, RAID50, PRL 11, PRL 11 with spanning,<br>
SRL 3 supported, PRL11-RLQ0 DDF layout with no span,<br>
PRL11-RLQ0 DDF layout with span<br>
<br>
That rebuild is far too long for comfort. Had another disk failed in those two days that would have been it. Neither controller has battery backup, and the one in question is not even on a UPS, so a power glitch could be fatal too. Not a happy thought while record SoCal temperatures persisted throughout the entire rebuild! The systems are in different buildings on the same campus, sharing the same power grid. There are no other backups for most of this data.<br>
<br>
Even though the controller shows this system as no longer degraded, should I believe that there was no data loss? I can run checksums on all the files (even though it will take forever) and compare the two systems. But as I said previously, the files were not entirely 1:1, so there are certainly going to be some files on this system which have no match on the other.<br>
<br>
Regards,<br>
<br>
David Mathog<br>
<a href="mailto:mathog@caltech.edu" target="_blank">mathog@caltech.edu</a><br>
Manager, Sequence Analysis Facility, Biology Division, Caltech<br>
______________________________<wbr>_________________<br>
Beowulf mailing list, <a href="mailto:Beowulf@beowulf.org" target="_blank">Beowulf@beowulf.org</a> sponsored by Penguin Computing<br>
To change your subscription (digest mode or unsubscribe) visit <a href="http://www.beowulf.org/mailman/listinfo/beowulf" rel="noreferrer" target="_blank">http://www.beowulf.org/mailman<wbr>/listinfo/beowulf</a><br>
</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr">- Andrew "lathama" Latham <a href="mailto:lathama@gmail.com" target="_blank">lathama@gmail.com</a> <a href="http://lathama.org" target="_blank">http://lathama.com</a> -</div></div></div></div>
</div>