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

[Valeri Galtsev]

On Fri, January 20, 2017 7:00 pm, Cameron Smith wrote:
> Hi Valeri,
>
>
> Before you pull a drive you should check to make sure that doing so
> won't kill the whole array.

Wow! What did I say to make you treat me as an ultimate idiot!? ;-) All my
comments, at least in my own reading, we about things you need to do to
make sure when you hot unplug bad drive it is indeed failed drive you have
to replace.

Valeri

>
> 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:
>
> OFFLINE A DISK
> MegaCli -PDOffline -PhysDrv[32:0] -a0
>
> MARK A DISK AS MISSING
> MegaCli -pdmarkmissing -physdrv[32:0] -a0
>
> MARK A DISK AS PREPARED FOR REMOVAL
> 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>
> wrote:
>
>>
>> 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
>>
>> > _______________________________________________
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>> > 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
>> ++++++++++++++++++++++++++++++++++++++++
>> _______________________________________________
>> CentOS mailing list
>> CentOS at centos.org
>> https://lists.centos.org/mailman/listinfo/centos
>>
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++++++++++++++++++++++++++++++++++++++++
Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
++++++++++++++++++++++++++++++++++++++++