On 2022-02-10 11:11 a.m., Matti Pulkkinen wrote:
TL;DR are there particular workloads that suffer from having to access
a RAID0 array?
I've currently got my /home partition in a BTRFS RAID0 array with two 1
TB mechanical drives, and I'm considering getting SSDs for /home
instead. I could get one 2 TB SSD and be happy with it, but I could
instead get two 1 TB SSDs and make a RAID0 array again. The latter
option would of course get me better overall throughput, but I'm
wondering whether there are workloads that might suffer from being run
from a RAID0 array vs. just running on a "bare" disk.
Read the SSD reviews before picking one. There are quite a lot of
variations in burst and sustained write speeds, number of rewrites
before failure, etc. There is even one out there that has performance
issues when you write the stupid flashy lights on it to a particular
colour (!!!).
SSDs have no appreciable seek time and have much faster read rates that
spinning rust. Depending upon how much onboard RAM cache they provide
(some even provide no cache), you may also see considerably better burst
write speed, although sustained write speeds are generally no better
than a disk. So, unless you are doing something that requires sustained
intense writes, moving to an SSD is a no-brainer. I would not bother
with RAID, as eliminating the seek times will speed up virtually any
app. Go with a single SSD because unless you are writing many TB/month,
a single SSD will also probably last longer than your spinning disks.
They also use less power and are quieter. IMHO, I think that LVM and/or
MD are a lot of extra and unnecessary complexity more useful on larger
servers (at least dozens of disks), and buy you very little on a smaller
server or personal workstation. If drive failure is a new concern
(remembering that you're using non-redundant RAID-0), then get a second
one and run them as a BTRFS or ZFS RAID-1 set.
P.S: Why are you using a RAID-0 array? You have no redundancy, higher
software complexity, somewhat better read speeds and much slower write
speeds, and a much higher chance of hardware error. RAID-0 is generally
used for things like very short-lived DB caches and not much else. If
you have a RAID controller, trash it, as the IOPS are inferior to
software solutions already in the kernel and FS logic. RAID rebuild
times with a controller are also generally so bad that you have
excellent odds that you will probably experience a second drive failure
while rebuilding with the drive sizes sold today.
--
John Mellor
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