ssd - Two SATA 2TB drives in RAID-1 configuration; only one 6.0gb/s port open

08
2014-07
  • Set Sail Media

    Here's the scenario:

    I am building a computer that will act as a network storage device for local networked users, and a source code repository and backup device for remote users. The machine will also be backing up to a third-party backup service (Carbonite) via internet connection.

    The machine contains (1) SSD drive, (2) 2TB HDD drives, and (1) DVD drive.

    • The SSD drive will contain the OS and program files
    • The (2) HDD drives will run in RAID-1 configuration (mirrored) and serve as data storage.
    • The DVD drive will seldom be used and is inconsequential.

    My motherboard has (2) SATA 6.0gb/s ports, and (4) SATA 3.0gb/s ports.

    My inclination is to use (1) 6.0/s port for the SSD drive. Since it's solid state, it deserves the faster port. But this leaves only (1) 6.0/s port open. I would like to take advantage of the other 6.0/s port, but not at the expense of the operation of the RAID configuration.

    Can I run the mirrored HDD drives, one on the (1) 6.0/s port left, one on an open 3.0/s port? Will this lead to problems in the short or long term?

    I don't know well enough about the mechanics of RAID... but I think I ought to put them both at 3.0/s, operating at similar speeds. My fear is that if I install them one at 3.0/s and the other at 6.0/s, and a user is writing a large file to the HDD drive, it will (in theory) take twice as long to write to the drive on the slower transfer port as it will the faster. And if this is happening simultaneously for many users, over long periods of time, the slower drive will be far behind, negating the benefits of mirrored RAID configuration.

    • Answers
  • David Schwartz

    You're okay connecting the two drives to ports at different speeds. Yes, it means that writes will be at 3Gb/s speeds, but reads will be at 9Gb/s speeds (assuming the drives can keep up), and you probably do a lot more reads than writes.

    It is never guaranteed that the two drives will stay in any kind of lock step. They're spinning at slightly different speeds, take slightly different times to seek, and so on. The RAID implementation knows how to deal with this.

  • Bradley Forney

    Just for my sanity and added redundancy I'd get a second SSD (since you seem to be running some critical stuff here).

    Put the two HDDs on the 3GB ports and install the OS there - RAID 1. Use this for automated backups during off-peak hours. Performance wont be a big deal for the process if it's all happening behind the scenes automatically.

    Put the two SSDs on the 6GB ports and make that your data partition - RAID 1. Use this for your code repo where your builds/commits/etc could result in a lot of active wait time. You want this to be as fast as possible.

    As for the network storage - this will depend on the usage. If you need more speed for the repo then toss the network storage onto the HDD array. If the network storage is going to need more speed and the repo is being used infrequently then it can share the SSD array.

    Also, depending on the amount of usage you may want to set the Carbonite setting for what I think is titled "Use less network resources" which will limit the bandwidth it consumes - saving it for what actually needs it on that box.


    • 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