IT Professionals

RAID Vs. SSD

Posted by on Aug 6, 2009 | 2 Comments

Gnomie Rafael Ramirez writes:

Hey, Chris. Lately I made up my mind on getting an Solid State Drive, but today I heard something that’s making me have a change of heart and I think it would make a great discussion video. I own a Mac Pro; obviously I would want an SSD for speed, but I would have to sacrifice space, which is also important to me. Today I found out that I could make a software RAID configuration using “Disk Utility” in Mac OS X — I did not know that. For the price of one 128 GB SSD (approx. $329) I could easily buy 3 1 TB Samsung drives ($102 from macsales.com). If I software RAID using using “stripped RAID set” in Disk Utility I could get 3 TB and a significant performance boost for the same money as an SSD.

Since you own an SSD I wanted to ask your opinion: Do you think SSD will run faster than three 1 TB drives in RAID? Maybe you could talk about RAID in general — forgive me if I’m wrong, but I don’t think it’s been mentioned? Anyway, some feedback would be appreciated. Here is a guide for making a software RAID on a Mac Pro; it’s actually quite easy to do.

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  • GiM

    This is where you need a PhD… :-)

    What is RAID: a component to allow a kind of PARALEL processing regarding storing data on heterogeneous memory drives (this is limited definition for your case).

    Even a software RAID should be close, some processing will be on your computer main processor and not on the hardware interface, but close enough.

    Now if you consider the evolution of SSD, how slow they were, how small they were… I was waiting to have a proper evolution and have “two power n” old SSDs working in parallel with a simplified and proprietary interface inside and ATA outside.

    You know, reading from a drive you read an “allocation unit size”, something of 512 bits multiplier minimum. Now if I have a modern well-designed SSD, it should contain 512 old slow SSD inside working in parallel, which means 512 quicker and 512 bigger…

    So, it should not be a speed problem for a really good SSD, theoretical they can reach something like 1,000 TB per second. Why the current SSD are really far from this, ask manufacturers…

    Now returning to your dilemma, you can have 3-4 small and cheaper SSD and use your RAID solution to have them working together. 32-64GB SSD start to be really cheap, so you can have 128-256GB at quad speed.

    If you count money, please verify first what is “bear necessities” and find that middle way for best price performance you need. If you don’t count them, just go for performance, a RAID with SSDs, it will be certainly “the best of the best”…

  • Chrystoph

    The thought that occurred to me in this instance was that you specify 3TB of storage. That suggests a RAID 0 (zero) configuration.

    http://en.wikipedia.org/wiki/RAID

    Please note, RAID 0 writes across all disks at the same time, spreading the write operation to make it quicker. The disadvantage of this is that it does not provide any data safety. If one hard drive dies, the data on all three is useless, as you have written part of it on all three drives. Think of it as writing the ABC’s on three pieces of paper. One letter goes on each sheet in order. If any sheet dies, you lose all of those letters.

    I would suggest that you ensure a RAID 5 configuration. This will provide 2TB of data, but still give you the RAID 0 write speeds. It also provides a method to recover should one of the drives die.