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PERC H310 Disk Cache Policy default
Hello
Pretty new to Dell servers so a steep learning curve here, please be patient with me :)
We have purchased an R320 server and decided on the PERC H310 controller and SAS disks for a RAID1 setup. In retrospect this may not have been the ideal controller, but it is what it is. Looking at improving disk performance (server is not heavily loaded, but suffers bad sequential write performance on large files causing occasional read timeouts for users).
I discovered the Disk Cache Policy was disabled and many have found better performance by enabling. According to what I heave read, disabled is default for SAS disks but enabled for SATA disks.
My question is... why? Why is the default different for the 2 disk types? I can't find any answer to this and I'd like to understand why Dell thinks it is better for SAS not to have disk cache policy before I go changing this setting.
I look forward to discussing this!
HuggaBounce
37 Posts
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January 31st, 2015 21:00
Guessing from the silence, nobody really knows :)
I even contacted Dell support on this. Which was awful. The "senior" tech firstly said the H310 doesn't have a write cache, which I promptly corrected him on (I asked about Disk Write cache, not Controller Write cache which the H310 has none, so already my confidence was lost with him).
The second response was the standard "enabling cache risks data loss in a power outage" which again is not even addressing the question. The tech then silently closed the incident without my agreement.
I speculate from his answer that this is not a technical decision, but a policy to help customers prevent data loss. Perhaps SATA Disk Cache was Enabled years ago for new RAID builds when SATA first came out and kept that way so there is a consistency with how configurations are delivered and behave. Realizing that not all customers have UPS this policy was changed for newer disk types.
Who knows, I don't, and don't care so much anymore since I have now turned it on and getting what I guess to be 10x better network write throughput. I expect if it was a bad thing, the controller would not allow it.
HuggaBounce
37 Posts
0
January 31st, 2015 22:00
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