[CentOS] CentOS 7 and Areca ARC-1883I SAS controller: JBOD or not to JBOD?

Sat Jan 21 01:00:04 UTC 2017
Cameron Smith <cameron at networkredux.com>

Hi Valeri,

Before you pull a drive you should check to make sure that doing so
won't kill the whole array.

MegaCli can help you prevent a storage disaster and can let you have more
insight into your RAID and the status of the virtual disks and the disks
than make up each array.

MegaCli will let you see the health and status of each drive. Does it have
media errors, is it in predictive failure mode, what firmware version does
it have etc. MegaCli will also let you see the status of the enclosure, the
adapter and the virtual disks (logical disks).

Before you pull a drive it's a good idea to properly prepare it for removal
after confirming that it's OK to remove it.

Here are a few commands:

MegaCli -PDOffline -PhysDrv[32:0] -a0

MegaCli -pdmarkmissing -physdrv[32:0] -a0

MegaCli -pdprprmv -physdrv[32:0] -a0

Here are some easy overview commands that I run when first looking at the
storage on a system:
MegaCli -AdpAllInfo -aAll |grep -A 8 "Device Present";
MegaCli -PDList -aALL |grep "Firmware state";
MegaCli -PDList -aALL |grep "Media Error Count";
MegaCli -PDList -aALL |grep "Predictive Failure Count";
MegaCli -PDList -aALL |grep "Inquiry Data";
MegaCli -PDList -aALL |grep "Device Firmware Level";
MegaCli -PDList -aALL |grep "Drive has flagged";
MegaCli -PDList -aALL |grep Temperature;

I also leverage MegaCli from bash scripts on my older Dell 11Gen that I run
in cron.hourly that check the health status of my arrays and email me if
there is an issue.

Cameron Smith
Technical Operations Manager
Network Redux, LLC
Cell:   503-926-4928

On Fri, Jan 20, 2017 at 3:38 PM, Valeri Galtsev <galtsev at kicp.uchicago.edu>

> On Fri, January 20, 2017 5:16 pm, Joseph L. Casale wrote:
> >> This is why before configuring and installing everything you may want to
> >> attach drives one at a time, and upon boot take a note which physical
> >> drive number the controller has for that drive, and definitely label it
> >> so
> >> y9ou will know which drive to pull when drive failure is reported.
> >
> > Sorry Valeri, that only works if you're the only guy in the org.
> Well, this is true, I'm only one sysadmin working for two departments
> here...
> >
> > In reality, you cannot and should not rely on this given how easily it
> can
> > change and more than likely someone won't update it.
> >
> > Would you walk up to a production unit in a degraded state and simply
> pull
> > out a drive and risk a production issue? I wouldn't...
> I routinely do: I just hot remove failed drive from running production
> systems, and replace with good drive (take a note what I said about my job
> above though). No one of our users ever notices. When I do it I usually am
> only taking chance of making degraded RAID6 (with one drive failed)
> degraded yet even more and become not fault tolerant, though still on line
> with all data on it. But even that chance is slim given I take all
> precautions when I am initially setting up the box.
> >
> > You need to assert the position of the drive and prepare it in the array
> > controller for removal, then swap, scan, add to virtual disk then
> initiate
> > rebuild.
> Hm, not certain what process you describe. Most of my controllers are
> 3ware and LSI, I just pull failed drive (and I know phailed physical drive
> number), put good in its place and rebuild stars right away. I have a
> couple of Areca ones (I love them too!), I don't remember if I have to
> manually initialize rebuild. (I'm lucky in using good drives - very
> careful in choosing good ones ;-).
> >
> > Not to mention if it's a busy system, confirm that the IO load from the
> > rebuild is not having an impact on the application. You may need to lower
> > the rate.
> Indeed, in 3ware configuration there is a choice of several grades of
> rebuild vs IO, I usually choose slower rebuild - faster IO. If I have only
> one drive failing on me during a year in a given rack, there is almost
> zero chance of second drive failing during quite some time (we had heated
> discussion about it once and I still stand by my opinion that drive
> failures are independent events). So, my degraded RAID-6 can keep running
> and even still stay redundant ("single redundant" akin RAID-5) for the
> period of rebuild, even if that takes quite long.
> Valeri
> > _______________________________________________
> > CentOS mailing list
> > CentOS at centos.org
> > https://lists.centos.org/mailman/listinfo/centos
> >
> ++++++++++++++++++++++++++++++++++++++++
> Valeri Galtsev
> Sr System Administrator
> Department of Astronomy and Astrophysics
> Kavli Institute for Cosmological Physics
> University of Chicago
> Phone: 773-702-4247
> ++++++++++++++++++++++++++++++++++++++++
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