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I have a p410i array controller that only has 256ram. We want to create a raid 5 so we have procured a 512 write back cache module.

If we install the write back cache, will this erase the existing raid information.

The server currently has 2 disks in raid 1. 6 are spare waiting for an upgrade to create a raid 5. the concern is if we replace/upgrade the memory for the controller, we will wipe the existing production raid 1 array.

Thanks in advance.

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3 Answers 3

Short answer is "no". HP array controllers do not store array-specific information only on the controller itself or its spare parts like writeback cache module, they produce a copy on the physical disks included into array. You can replace cache module, add/remove memory or replace the controller entirely (due damage or other reasons) - the array configuration will be read from the disks automatically.

You may consult HP Instant Support here: http://h50203.www5.hp.com/hpisweb/customer/AdviceDisclaimer.aspx?option=activechat for more details.

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Cache memory addition/removing have nothing related to disk contents (arrays).

Cache memory in the controller enhances read and write performance, improving overall storage throughput. Streaming data can be queued into the cache to dramatically accelerate read performance. Sophisticated algorithms measure data patterns and usage, dynamically re-allocating read cache to achieve optimal performance.

So you can feel free to upgrade cache memory on controller - no any data loss will occur and performance should be improved with more cache size.

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When you add RAM and a battery-backed or flash-backed cache unit to a Smart Array P410 controller, you will gain write performance and unlock a few features. You'll be able to perform an array transformation (e.g. convert from RAID 1 to RAID 5) online. And yes, you're correct. RAID 5 is not available on Smart Array P410 controllers that do not have a cache and battery combination. Other than that, the controller and the RAID array data is unchanged.

My usual warnings apply: You should perform this work using the HP Array Configuration Utility, either offline from the HP SmartStart CD, or with the HP ACU utility for your operating system.

Please update the firmware of your controller.

Each revision of the firmware adds functionality and fixes bugs. It's usually a good idea to do this.

Also, while I know your goal is RAID 5, have you considered RAID 1+0? If speed is more important and capacity isn't an issue, I would definitely choose RAID 1+0 over RAID 5 in that setup. See the canonical RAID discussion for more detail.

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hi, thanks everyone for the responses. Raid 5 for redundancy only. Performance isn't a big factor. Thanks again. –  James Sep 16 '12 at 3:43

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