On Fri, September 8, 2017 12:56 pm, hw wrote:
> Valeri Galtsev wrote:
>>
>> On Fri, September 8, 2017 9:48 am, hw wrote:
>>> m.roth@xxxxxxxxx wrote:
>>>> hw wrote:
>>>>> Mark Haney wrote:
>>>> <snip>
>>>>>> BTRFS isn't going to impact I/O any more significantly than, say,
>>>>>> XFS.
>>>>>
>>>>> But mdadm does, the impact is severe. I know there are ppl saying
>>>>> otherwise, but I�´ve seen the impact myself, and I definitely
>>>>> don�´t
>>>>> want
>>>>> it on that particular server because it would likely interfere with
>>>>> other services.
>>>> <snip>
>>>> I haven't really been following this thread, but if your requirements
>>>> are
>>>> that heavy, you're past the point that you need to spring some money
>>>> and
>>>> buy hardware RAID cards, like LSI, er, Avago, I mean, who's bought
>>>> them
>>>> more recently?
>>>
>>> Heavy requirements are not required for the impact of md-RAID to be
>>> noticeable.
>>>
>>> Hardware RAID is already in place, but the SSDs are "extra" and, as I
>>> said,
>>> not suited to be used with hardware RAID.
>>
>> Could someone, please, elaborate on the statement that "SSDs are not
>> suitable for hardware RAID".
>
> When you search for it, you´ll find that besides wearing out undesirably
> fast --- which apparently can be contributed mostly to less overcommitment
> of the drive --- you may also experience degraded performance over time
> which can be worse than you would get with spinning disks, or at least not
> much better.
Thanks. That seems to clear fog a little bit. I still would like to hear
manufacturers/models here. My choices would be: Areca or LSI (bought out
by Intel, so former LSI chipset and microcode/firmware) and as SSD Samsung
Evo SATA III. Does anyone who used these in hardware RAID can offer any
bad experience description?
I am kind of shying away from "crap" hardware which in a long run is more
expensive, even though looks cheaper (Pricegrabber is your enemy - I would
normally say to my users). So, I never would consider using poorly/cheaply
designed hardware in some setup (e.g. hardware RAID based storage) one
expects performance from. Am I still taking chance hitting "bad" hardware
RAID + SSD combination? Just curious where we actually stand.
Thanks again for fruitful discussion!
Valeri
>
> Add to that the firmware being designed for an entirely different
> application
> and having bugs, and your experiences with surprisingly incompatible
> hardware,
> and you can imagine that using an SSD not designed for hardware RAID
> applications with hardware RAID is a bad idea. There is a difference like
> night and day between "consumer hardware" and hardware you can actually
> use,
> and that is not only the price you pay for it.
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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
++++++++++++++++++++++++++++++++++++++++
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