Stephen John Smoogen wrote:
On 13 September 2017 at 12:00, hw <hw@xxxxxxxx> wrote:
It will depend on the type of SSD. Ones with large cache and various
smarts (SAS Enterprise type) can take many different sizes. For SATA
ones it depends on what the cache and write of the SSD is and very few
of them seem to be the same. The SSD also has all kinds of logic which
moves data around constantly on disk to wipe level so it makes it
opaque. The people who have tested this usually have to burn through
an SSD set to get an idea about a particular 'run' of a model but it
doesn't go over every version of the model of SATA SSD.
Hm, so much to SSDs ... I can only hope they will be replaced with
something better.
I have decided against putting anything onto these SSDs other than temporary
data, but even for that, I would need to make an md-RAID, which I don´t
want.
It may work or not, and "may work" is not enough.
May work is part of any commodity hardware build. The SATA hard drives
do not use the same technology as 4 years ago and you may end up with
them having crap out on shorter lifetimes because they aren't built to
live longer than 3 years depending on the model. [It doesn't matter
the brand.. they get built with the same tech and at the same place
these days.]
Spinning disks don´t have the trouble with writing as SSDs have, and they
are used for hardware RAID in this case. The SSDs may work with hardware
RAID or may not. They may work for their purpose or they may not. The
spinning disks will work, they have done so for the last two years ---
with ZFS rather than hardware RAID, but WD Reds should do fine, and do
so since about a month now.
My experience is that spinning disks fail either within the first three
months or when about three years old --- or virtually never because they
get so old that they are being replaced by disks with greater capacity
before they fail.
Nowadays, what isn´t build to fail as soon as the manufacturer can get
away with? :( Even cars you pay 70k for are built to fail after only
three years, same as those that cost 256k used. (The 256k one I saw at a
BWM dealer, and the sales guy told me they are built to fail. Go figure :) )
If the performance on the hardware RAID isn´t as good, it can not get worse
than it is now, and it may be even better than with the SSDs.
I have two at home with the system installed on btrfs. I´m going to change
that
to md-RAID1 and xfs. Is there anything special involved in copying the
system
to another disk? Will 'cp -ax' do, or should I use rsync to copy xattrs
etc.?
Using the commonly used stripe size of 128kb is something I´d expect the
SSDs
being able to handle.
Depending on what CentOS you are working, cp -a will preserve xattrs.
Centos 7
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