On Wednesday 2017-12-13 15:29, cagsm wrote:
Date: Wed, 13 Dec 2017 15:29:54
From: cagsm <cumandgets0mem00f(a)gmail.com>
To: "opensuse(a)opensuse.org" <opensuse(a)opensuse.org>
Subject: [opensuse] Raid, Raid6, what file system for good fault tolerance?
speaking about software raid, not hardware controller based.
I am trying to go for some local OpenSuse machine and adding some
storage to it. Was considering Raid6, and now reading about a bit and
people left and right scaremongering about the larger the disks these
days in the double digit terabyte capacities even, the more likely it
is that during a reconstruction of a raid subsequent errors would
I would absolutely like to keep my data consistent, and I am not
thinking about double digit terabytes either, would stick to 2TB or
4TB disks, with Raid6 thats at least 4 physical drives.
Now I am wondering if it possible to use a good robust file system
that can add some more parity or check blocks or redundancy on top of
the hardware disks, to absolutely be able to always read my data.
I can't add multiple machines or like those high availability stuff
like clusters and what not I read about DRBD (Distributed Replicated
Block Device), or maybe I am just too scared by those technical terms
or consider myself to be just a simpleton and wanting to keep it
My use case here is also not constant availablity, when a disk needs
to be replaced, so be it, but I don't want to lose my data that I can
not ever read certain parts of it again or such stuff.
The thing that came to my mind was, if there is some file systems that
would add redundancy and robustness onto the mdraid system of the
Anyone with some useful insights? Roughly speaking, I was considering
some simple pcie esata interfaced controller card and an external case
enclosure with esata port and portmulitplier stuff inside, that can
present at least 4 physical disks as JBOD, just a bunch of disks, so
that the Linux can seem them all separately.
Speed and rebuild times are not my concern, but data persistence and
data integrity. Not even number of physical disks, I could live with
even one of those 8 bay device enclosures and cases that are out there
on the market.
I have very good experience using RAID 10 for more than 15 years at low
cost. Never had data loss.. any journaling filesystem is good. In the
past I also used reiserfs, but had the most problem with it.
These eSATA enclosures are quite cheap and handy.. 4 disks per
enclosure, per eSATA-connector.
The HDDs I use are targeted for video or server appliances (24/7
running, very high MTBF), most important, that all(!) hdds have the same
geometry, preferably same model and same fw-revision. Keep invoices for
RMAs.. Over the years I have got around 30 RMAs..
RAID 10 is very robust, additionaly I always have a hot spare, so up to
3 out of 5 disks could fail under perfect circumstances.. i think cpu
load is way lesser than using RAID5 or 6..
an alternative to mdadm software raid could be btrfs raid, but have only
experience with RAID 1, and it seems to lack hot spare support.
Most sata port multipliers allow also software SMART monitoring.
My most recent bought (internal) multipliers also support real hardware
raid, but I did not switch yet (maybe on next HDD upgrade, to give it a
For scalability I also use LVM. Currently I am using EXT4 and XFS
filesystems. Never had problems at all on software side. Problematic
were cheap SATA-cabling (bad shielding, bad connectors) - very important
beside monitoring pending sectors of course is to monitor
UDMA_CRC_Error_Count and Load_Cycle_Count. First are an indicator for
electromechanical problems and second, power supply - those degrade by
time, so I am also monitoring voltages via ACPI.
But most important, still: backups. Cheap solution consumer level big
HDD. I do daily incremental backups, using two HDDs, which are
exchanged regularly (currently weekly) and store the unused one at an
fire safe storage place.
Best would be a modern LTO-6 or LTO-7 tape drive with loader... but
that's unaffordable at the moment..
Just my experience and tips
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