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I have HP DL380p G8 with smart array P421i.

I would like to use SSD cache for my HDDs RAID 10 volume. I got know I have to buy a SmartCache license for the array and I found some weird info about the posibble configuration of this cache. I cannot ask for HPE support because of expiration warranty.

Can I use 2 SSDs in RAID 1 and use this as a cache? Somewhere I found in GEN8 I can use only the RAID 0 for the cache.

If not, how does it act if I use only 1 SSD as cache and it fails, does the data fail or what could happen? Or does it use just a read cache so nothing happens to the data?

My information source: https://www.hpe.com/us/en/product-catalog/detail/pip.5364342.html#

Thank you.

Garen

Garen
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2 Answers2

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I am not familiar with HP smart array raid controllers, but according to my experience with CacheCade technology on LSI/Avago Raid-controllers single SSD will work only in Write-Through mode, 2x SSD's in RAID-1 will work in Write-Back mode and 2xSSD's in RAID-0 will work in Write-Through mode. Moreover, you can try this Elitebytes Velossd (https://www.elitebytes.com/) to achieve flash caching on software level or these guys StarWind VSAN Free (https://www.starwindsoftware.com/starwind-virtual-san-free) which actually has a free version of the software.

Strepsils
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My recommendation:

Skip the SSD cache on a Gen8 server... The solution isn't easily monitored and I've found it to be of questionable use for MY workloads. But to answer the question, you would stripe multiple SSDs. There's no RAID1/mirroring of them.

If you need the performance, it may be better to consider faster/more disks than relying on the SSD read cache. Or maybe an all-SSD array.

  • How big is the array?
  • How big is the SSD?
  • How many 10k/15k disks do you have?
  • Do you know what the working set of data is?
  • Is this a workload that can benefit from read acceleration?
ewwhite
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  • The main reason to use the SSD cache is because there are just 7200rpm HDDs. – Garen Feb 01 '18 at 07:44
  • How many disks? What is the workload? What will the usable capacity of the array be? – ewwhite Feb 01 '18 at 07:53
  • The main reason to use the SSD cache is because there are just 7200rpm HDDs. Right now 6x WD Gold 6TB in RAID10. SSD is Samsung Pro 256GB There will be an ESXi server with Oracle servers and some testing servers. As I know it depends on the memory with Oracle, if there is enough memory, it wont use the disk as much... – Garen Feb 01 '18 at 08:20
  • Does this server have 3.5" LFF disk bays? – ewwhite Feb 01 '18 at 13:16
  • Yes it has LFF bays. – Garen Feb 01 '18 at 15:14