hard drive - Reliability of 4 SSD in RAID 0 -vs.-SSD Boot+5440 HDD - in laptop

08
2014-07
  • Doctor Whom

    Question: What are the benefits of SDD RAID 0 over SDD boot with 5400 HDD?

    Goal: Decision between internal storage options

    Needs:
    Ability to seamlessly use multiple graphics and coding programs simultaneously.
    Reliability of data in between backups - considering it is a mobile laptop.

    Options being considered: 4x 256mb SSD in RAID 0 -vs.- 512mb SSD mSATA boot + 512mb 5400 HDD (Single large SSD is not an option available.)

    Questions:

    • Assuming reliability is more important than speed, is there a benefit to the RAID 0 arrangement over the SSD boot with regular HDD?
    • Acknowledging that RAID 0 has no redundancy, my reliability question hinges on the fact there are 4 disk drives versus two. SSD reliability in comparison with HDD seems to be not very different.
    • When a disk fails in 1 SSD among 4 in RAID 0, does it risk damaging data on the other 3? Loss of 25% rather than loss of 100%?
    • When an disk fails in the SSD (or HDD) of a SSD + HDD, does it only lose data on that disk? 50% vs 100?
    • In these cases, would 2 drives always be better than 4?

    (My primary question is comparison of reliability of arrangements. I was unable to find a comparison of this combination elsewhere.)

  • Answers
  • Michael Kjörling

    Assuming reliability is more important than speed, is there a benefit to the RAID 0 arrangement over the SSD boot with regular HDD?

    NO! RAID 0 is striping without parity or redundancy. If any of the constituent devices in a RAID 0 array fails, then the entire array fails and cannot be accessed by normal means. It won't really "damage" the other devices, but you won't be able to get anything useful out of them by normal means either. Since you have four times the number of devices in the four-device array, as techie007 also pointed out your total failure odds instantly at least quadruples (possibly more, since you have four devices hooked up to the same power and data buses).

    RAID 0 provides speed and/or storage space advantages, at the cost of reliability. If you want reliability, then you need to use something else.

    It doesn't matter whether the constituent devices are solid-state or spinning-rust storage devices; RAID 0 is still RAID 0. A RAID 0 array fails if any constituent device fails or becomes unavailable; period.

    If you want reliability beyond what a single device can offer, then your best choice on a laptop is probably mirroring. Mirroring also has the potential to increase your read performance, as any read can be satisfied equally by any constituent device. RAID 5 or 6 would work as well but require at least 3 or 4 devices to provide any benefit, and have their own potential problems (think RAID write hole).


  • Related Question

    ssd - Which Hard Drive Configuration on a new Computer?
  • aceman

    I'm planning to buy new computer, but suddenly I found myself confusing regarding hard drives. I want a FAST AND SECURE way to store my data, but at the same time cost effective. This is going to be my workstation/development machine and I am asking this because I always had bottleneck problems with hard drives.

    First I was thinking to construct RAID 1+0 or 0+1, but later I found out that RAID 5 can be more cost effective because it only needs 3 drives instead 4, but i don't know about performance gain/hit.

    I was also thinking to buy a 60GB SSD hard drive and use it only for Windows installation. All other programs, etc., I would install on another disk and then I also would have a third drive to save static data like downloads, movies, installation files, ISOs, etc.

    I am really confused which option to use here, or is there even some better configurations that I am not aware of? Any suggestions?


  • Related Answers
  • 8088

    I like the SSD + large hard drive idea the best: fast OS operation + large storage. For cost savings, you may consider the 10k RPM WD Velociraptor instead of the SSD. For backup, I would use a drive external to the system, either a USB drive or a NAS.

    RAID is more trouble than it's worth for this. It's a solution for servers to prevent downtime; typical desktops don't need that. Even mirroring doesn't provide the same advantages that a true backup would.


    To address the SSD vs VelociRaptor issues:

    Intel X25-M 80GB SATA II SSD, USD 310 (Intel was Anand's recommendation)

    Western Digital VelociRaptor 150GB 10k RPM SATA 3.0Gb/s, USD 180

    alt text

    The Intel SSD is almost 2.5 times faster than the VelociRaptor in this particular test. It's also over 3 times more expensive in cost/GB. You'll just have to pick what's more important to you.

    For large storage, Ars Technica recommends

    Western Digital Caviar 1TB 7200 RPM SATA 3.0Gb/s, USD 95.

    Notes:

    • More charts at Anandtech, The SSD Relapse: Understanding and Choosing the Best SSD
    • Futuremark's PCMark whitepaper
    • Prices are from http://www.newegg.com and only valid at time of writing
    • It's been shown that the SSD advantage is not quite as significant in large sequential writes, but (1) some benchmarks still show them coming out ahead in this area and (2) it does not represent the majority of usage.
    • For now, only Windows 7 (and Solaris?) claim they optimize for SSD's. Future benchmarks may show even greater performance. On the other hand it's a young technology and we're not sure what impact wear-leveling will have on long term performance or reliability.
  • ted_j

    If cost is no object, get a nice enterprice class SSD and put all OS/App stuff on that, a two-drive striped RAID for workspace, and an external backup drive.

    Have a VelociRaptor or equivalent, either single-unit or striped two-drive RAID as the data-only drive.

    Have an external eSATA or USB2 device with a 1-2 TB drive as backup space. Once the machine is installed and ready for work, image the system drive onto it. Make a regular habit using any decent backup software to backup data-only drive onto it (maybe nightly, automatically).

    I'd put the TEMP folder on the working drive, maybe. I know that the SSD would probably be better in raw speed, but small temp file activity that is immediately read back may never get outside the drive cache and will then save you wear-and-tear on the SSD.

    The reason I say to put the app intstalls onto the SSD is that the way most apps are loaded these days their image files are virtual-memory mapped, and never wholly paged into memory. This means they end up extensions of the virtual memory subsystem, and while VM systems tend to perform great it'll r0x0r with the random-access speed of the SSD. This also removes device contention from your work drive, allowing you even more effective throughput on it.

  • Doltknuckle

    When it comes to the question of using an SSD, @hyperslug has a good answer with lots of information about SSD and 10K drives. When designing the storage solution, you need to make sure that your hardware matches your use case. Here's a break down of the potential options:

    SSD Drives

    • Fastest read/write/seek times you can get on a drive.
    • Limited number of write operations.
    • High cost and low capacity right now.
    • Silent
    • Full drive encryption has some problems (source, but do a Google search for more info)

    10K Drives

    • Faster than a normal hard drive, but slower than an SSD.
    • Essentially unlimited number of writes.
    • Better Dollar per GB ratio than SSD.
    • Generally the loudest drive

    Standard Hard Drive

    • Slowest of the drives
    • Best Dollar per GB ration
    • Can be quieter and draw less power than a 10K drive
    • Best for medium to long term storage.

    So what do you pick? Well it depends. In most cases, an SSD as your boot drive will do the most to increase your start up time and general performance of the system. This can be done with a relatively small (read cheap) SSD. The problem is that if you get too small of an SSD, you have to place your programs on another drive. When you do this, you will loose many of the speed boost that an SSD can give you in the terms of application launch times. Once the application is in memory however, the program should be running from memory and not have to access the hard drive that much. If application launch times are important to you, then moving that information to an SSD may require a bigger (more expensive) SSD.

    But what about your data? Where do you put that? Depending on the size, you may be forced to leave it on a spinning disk. If the files are relatively small, you can keep your current project on the SSD and move files off on and off the drive at the start and end of the project.

    Finally, what about security? If someone steals the computer, they can simply plug the drive into another computer and pull all of the data off the drive. One method of protecting against this is whole drive encryption. This makes sure that when the attacker looks at the drive, all they see is pseudo-random noise. The problem is that this type of encryption is not suited for an standard SSD. I have heard of self encrypting SSD drives, but have not tried them out myself.


    So bringing this all back together, here's my recommendation based off of what I think you need:

    Start with an SSD. Get one big enough to put at least your OS and Programs on it. Make sure to have at least 10-20GB free so you don't constantly have to work in a constricted environment. Get a large standard hard drive and put all of your data on that drive. Use full drive encryption on the storage drive to protect your data.

    Once you have the system built, use it for a month and reevaluate if you need more performance. If you feel you need more speed, without sacrificing security, get a 10K drive and use it as a scratch drive. Use that for another month and then reevaluate.

    Assuming you need more power, find a self encrypting SSD and replace the 10K drive with it. If you need more than that, you'll have to start looking at some really expensive equipment that is outside of the scope of this answer.

    It's important to remember that speed and security costs money. The trick is to find the balance that maximizes your buying power.

    Hope this helps