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HP P420 and HP SmartCache

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fce2
Occasional Collector

HP P420 and HP SmartCache

Hi,

it's my 1st post here, i hope i do everything right ;-)

I own a very small but really nice and powerful HP server.
Here is my setup:
HP Microserver Gen8 with a Xeon E3-1240v2 and 16GB and iLO Advanced
HP P420/2GB with 4*5TB Seagate Enterprise Capacity (in Raid-5) and 4*500GB Samsung EVO 850 and SAAP 2.0

For the P420 i've bought and installed the SAAP 2.0 and I want to use SmartCache feature now.
I've learned that (for the P420) only a SSD-Raid-0 cache in write-through is possible, and this looks good and safe for me.
Raid-0 with 4 SSDs is really fast. I tried a "normal" (non-cache) raid-0 drive and did some read and write benchmarks on this drive with >2GB/sec !! very impressive ! Btw. Raid-5 write performance breaks totally down, just 300MB/sec, but thats not a problem for this post ?!?
Write-Trough instead of Write-Back is ok i believe, this always should be safe even on a power-loss condition.

Now to my question:
I played a little bit with the SmartCache and removed the cache-SSD (I was playing with an old SSD).
Then i got this message: "All data on this logical drive has been lost." !!! So ireplaced the SSD, and happyly the data on the HDs still were availble (I'll never try this with my "hot" data again, i nearly got a heart attack) !
So what happens if a Raid-0 cache failes ??? Is my data on the Raid-5-HDs in danger ? Or is my data safe and only the Raid-0-Cache is broken and the cache just can be deconfigured or a ssd has to be replaced and everything is still available ?
I believe this is the case, but I'm not sure and the error message I described before really scares me !
I tried to get and read all info/manuals/howtos/... But even in official HP manuals I did not find an answer, just some notes like "Specifying the write-back cache write policy when using a RAID 0 cache volume could result in data loss in the event of failure of the cache volume."... Well,  they explicitely write "write-back" !!

Any idea if my assumption is right and i can use the SmartCache feature without danger ?
(Otherwise this feature would be unusable for mostly everyone !)

Thanks for all answers and suggestions !

4 REPLIES
fce2
Occasional Collector

Re: HP P420 and HP SmartCache

Hmmm,

nobody ever used SmartCache ?

fce2
Occasional Collector

Re: HP P420 and HP SmartCache

Another "Hmmm"...

why was my question moved out of "storage" ?? 
its not a "netserver" problem, its a storage thing ?!?

 

Torsten.
Acclaimed Contributor
Solution

Re: HP P420 and HP SmartCache

Please read the first page

http://www8.hp.com/h20195/v2/GetPDF.aspx/c04123148.pdf


Hope this helps!
Regards
Torsten.

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fce2
Occasional Collector

Re: HP P420 and HP SmartCache

Hi Torsten,

thanks, yes helps a lot !

1) I was a little bit blind
2) I was afraid of the error message i got on my 1st test "All data on this logical drive has been lost" since it was not clear for me which LD was meant !!!

So i'll enable SmartCache and hope its like i expect: perfect safe and just fast !