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Another Hard Drive Bytes The Dust, But Is It A Momentus Moment?

HP dc5750 desktopIf I may take a moment to anthropomorphize…hard drives are not immortal. I was reminded of this very fact when overnight on April 11th a drive in my primary desktop failed.

Given that I was just one day away from my making annual forced trek to Las Vegas for the NAB Convention, and the fact that our income tax return was on that media, it certainly could have been a a problem. However, it wasn’t a catastrophe. Not at all.

The two computers that Stella and I use as our primary desktops sport internal RAID 1 disk arrays. Both desktops came that way. In fact, that was part of their appeal. I was concerned that Stella would have a drive fail one day when I was travelling. Such a failure at an inopportune moment would surely heap calamity upon my very existence.

These desktops are now getting older. Last fall Stella’s system did lose a disk. She told me about the event, advising that she received a desktop prompt noting that “Logical Drive 1 had become critical.” I said not to worry, if it was still running it wasn’t being critical of anything she had done. All would be well until I resolved the trouble.

In the more recent case of my desktop one drive simply failed. I just removed the bad drive. When the system rebooted it was functional but operating very slowly. I thought that the RAID controller was surely suffering the loss of one of its mates, and that a new drive would solve the problem.

However, replacing the failed drive proved troublesome. I added a new, bare disk of the same size and brand as the old one. The embedded RAID controller attempted to rebuild the array but kept failing. Thus I was still operating from a single disk.

In the end I cloned the failed RAID volume onto the single new disk, configuring it as a JBOD via the disk controller. I was forced to leave the system in this state as I left for NAB. The system was nominally functional, if unprotected.

While travelling I pondered my experience with the system since it was new, and now operating from the single drive. You may not initially consider this, but a RAID 1 array offers twice the read performance of a single disk. Write performance is about the same same as a single drive, but reads are much faster.

Drive performance was not something that I had previously considered. I had selected the RAID 1 arrangement for its fault tolerance attributes. I now suspect that the RAID performance has been part of what has kept us from suffering the systems age. Operating from a single drive it’s markedly less zippy in everyday tasks.

Seagate Momentus XT 750 GB 250pxAs you may recall a year ago I did some minor updates to my company issued laptop. It was effort to make it more serviceable in the light of its age and the reduced likelihood that it would be replaced. That effort included moving to a 500 GB Seagate Momentus XT hybrid hard drive. That drive was a nice step up from the stock drive and has been performing well this past year.

Examining the pair of 3.5” format hard drives in the desktops RAID I find that they were sandwiched tightly together and ran fairly warm. Heat is possibly the worst enemy of a hard drive. This caused me to consider alternatives.

I was wondering if there might be some wisdom in replacing the drives in the RAID with a pair of Seagate Momentus XT 750 GB hybrid drives. Their 2.5” design stems from the requirements of laptops, including lower power consumption and limited heat output. A pair of 2.5” drive could be mounted in an adapter that is the same size as one standard 3.5” drive.

The drives that were in the failed RAID were reportedly capable of 126 MB/s sustained transfer from disk to interface. In contrast the current generation of Momentus XT is rated at 112 MB/s. Thus the aggregate performance of the pair of Momentus XT drives might be slightly less than a pair of 3.5” 7200 RPM drives for sustained transfers.

Their on-board flash storage should make them considerably faster than the older disks for small file access, especially the most commonly read files.  Of course, at $152 / 750 GB the hybrid drives cost more than traditional drives, but not as much as a pure SSD.

Another alternative might be an SSD as boot drive, adding a traditional disk for additional mass storage. That would not have the fault tolerance of the RAID 1 arrangement.

Then again, I could select a pair of WD VelociRaptor disks. We’ve made great use of these in the products that my employer manufactures. Their 10k spin rate provides great performance, although they are typically smaller than comparable 7200 RPM disks at the same price point.

Or perhaps I should junk the old desktop entirely and get a new one? That seems wasteful and potentially costly.

Hmm. Decisions. Decisions.

On my recent trip to the UK I noticed that many of my co-workers use only a laptop, often augmented by a docking station. I still found that arrangement confining. I wonder if the very fact that I still like to have a desktop and laptop makes me a dinosaur?

Well, at least that’s been decided.

Update: May 1, 2012 – In a fit of pure “Oh, what-the-heck, let’s-just-try-it” I’ve procured another Seagate Momentus XT 750 hard drive. Now that I have two of these little beasties I’m planning on recreating the RAID1 setup using the hybrid drives.

For the moment I’m cloning the current instance of the system to a plain vanilla 750 GB drive. Once that’s done I’ll create the new RAID set and return the image to that volume.

There are gigabytes of data moving in various directions around here today.

Update: 9am, May 2, 2012 – Yesterday I was able to clone the system to a single 3.5″ desktop drive. Then I configured the pair of Momentus XT 750 drives as RAID1 in the RAID BIOS. At around 7pm I started the system cloning the single drive onto the RAID1 set using Acronis Migrate Easy.

That cloning activity ran overnight, and to my surprise is still running! It’s presently 81% through moving the volume to the RAID set.

While the write performance of the Momentus XT drives is no better than a single drive I would have expected the process to complete overnight. The volume being cloned is 750 GB (699 GB formatted) and has about 510 GB of data.

Update: 1pm, May 3, 2012 – My little experiment seems to be a failure. Apparently the RAID controller has issues with the hybrid drives. When the running image of the system was cloned to the RAID1 set it ran unbelievably slowly. Not only did cloning the system take over 13 hours, but after it booted….yes, it booted fine…it ran with all the speed of an advancing glacier. Disk access was reduced to speeds not seen since ZIP drives were popular large format removable media.

I’ll use the Seagate hybrid drives in other roles. Having spent a considerable sum to acquire that pair I’m now going a cheaper path to put traditional 3.5″ disks into the old desktop. I’m recycling some 500 GB Hitachi drives that came from our NAS device in its last upgrade. These drives are older but should suffice for as long as the desktop remains in service.


This Post Has 3 Comments
  1. Thanks for the article. I have been thinking of doing the same thing. I thought I might mirror my current drive to one of the new drives, boot and run OS, shut down, install other hybrid drive and configure RAID 1 in Device Manager. 

    1. Last month I replaced the older HP desktop in question. Instead of a RAID1 arrangement this time I went another direction. I bought a retail desktop that was a good deal.Then I cloned the boot volume onto an SSD and used the 2 TB drive for mass storage. It’s easy enough to image the SSD since it doesn’t have tons of user data.

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