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Storage array: Bare drives, SS, RAID, SSD, or other?

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October 25, 2009 7:44:32 AM

Obviously the basic hierarchy would go SSD(Intel x25-m; OCZ) > 10k(Velociraptor) > 7.2k(Spinpoint F3; Caviar Black; Barracuda) > 5.4k(Caviar Green), but I am curious to see the relative performance of these drives when short-stroked or put into a RAID array so that I can better decide which combination of storage devices would be of the greatest benefit to me, with price and hassle of course factored in. General ideas are welcome, but I believe what would help me the most are benchmarks and numbers and graphs.

Thanks.
a c 415 G Storage
October 25, 2009 4:52:39 PM

I'm not going to comment on the relative merits of the options you've given, but I want to point out that when you read other posters replies or look at benchmarks you have to understand that there are different ways to measure performance, and you need to know what they are and how they relate to the type of performance you are trying to evaluate:

Transfer rate - how quickly a long stream of data can be moved to or from the drive. Important for copying large files or running programs that use large files (ie, Photoshop reading RAW picture files, video editing, etc.) Typically measured in MB/sec.

Access Time (also known as "Latency") - how much time it takes from the time an I/O is requested until the data is delivered. Important when you need to read a LOT of files, such as when booting the system, loading applications, or running programs such as a browser which use files for caching. Sometimes measured in MB/sec, but probably better compared as IOs/sec.

Concurrent I/Os - how many I/Os can be handled simultaneously. Important when multiple users are accessing a server, when you're running multiple programs that access the same disk at once (i.e., virus scanning). Measured as IOs/sec.

As a general rule, RAID can improve transfer rate and concurrent I/Os but can't do much if anything for access time. Disks that spin faster have faster transfer rates and access times. SSDs are about 100X faster than hard drives in terms of access time.

People have a habit of focusing on one or another of these metrics which leads to conflicting advice and arguments...
October 25, 2009 5:32:03 PM

Thank you. If what you say is true, I would estimate that transfer rate would not be as helpful as access time. I would not be copying files very often (I'm not even sure I want to back everything up), and I'm not using this PC as a host or head unit.

That was a very helpful reply.
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