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September 29th, 2020 17:00
How to get more write cache on PERC?
I have a R720XD with a PERC H710P
I am working with large virtual disks (50+TB) in RAID5 and large files (30-40GB each). When copying these large files from SSD virtual disks over to the HDD virtual disk, I am maxing out the 'active time' of the windows volume and its taking 20 minutes sometimes to write a 40GB file.
The H710P has onboard 1GB cache, but I need more. I have plenty of SSD capacity (hundreds of GB) and I'd like to figure out how to get the PERC to use SSD's for write cache.
Everything I read about CacheCade says its for read caching only. How do I get the PERC to use SSD's for write cache? I need write cache upwards of 50-100GB. That way, an entire 40GB file copy could complete quickly in the write cache, and then write to the slow disks over time while the entire virtual disk doesn't lock up because its busy.
aryzen
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September 29th, 2020 20:00
I am not aware of any solution that exists within Dell's hardware scope for such big caches and hope Dell staff can suggest it since I am very interested as well.
However, what people in my company use is bcache on 1TB NVMe disks attached to the PCIe slots, which is a robust and efficient solution independent of hardware manufacturers. It permits creating write caches for any kind of disk/array configurations, with a lot of tuning options (writeback amount, other caching modes, etc)
bcache is only available in all major Linux distributions, but there is a similar solution for Windows called Intel Smart Response, on which I can't provide any feedback due to lack of experience.
DELL-Joey C
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September 29th, 2020 23:00
Hi @lanman9000,
Well yes, you're correct, H710P is able to do CacheCade but it's only read cache only unfortunately. I can't think of any way to add write cache for your server at the moment. Probably you can try suggestion by aryzen.
lanman9000
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September 29th, 2020 23:00
The Server is running VMWare ESXI 6.7 U3.
I need something that can work at the hardware layer (or be supported natively in esxi)
Also, I don't understand CacheCade being read only cache. According to LSI using cachecade for writecache has been available since 2011.
https://searchitchannel.techtarget.com/news/2240039368/LSI-MegaRAID-CacheCade-gets-write-caching-capability
How has this functionality not made it into the dell firmware?
DELL-Joey C
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September 30th, 2020 02:00
Hi,
I don't have the access to the design engineering, I couldn't get an answer for your question on it. Though in the article, it's on specific LSI IO controller model, for H710P it's using a LSI 2008 chipset. And I'm unsure if it's more to hardware controls or it's a software control mentioned in the article: LSI MegaRAID CacheCade Pro 2.0.
I tried googling, and I got this: https://dell.to/3cJNuQn
Let me know your thoughts.