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Surge

Pony Tails

Here’s a veteran systems administration move that not a lot of people know about. Though to be honest I haven’t really asked around to find out if people know about it or not; that’s not so much beside the point as it is back in the cheap seats on the point’s reunion tour, obviously. It’s also counterintuitive, this year’s soi-disant-intelligentsia shorthand for “fashionable”, so between that and the exclusivity of ignorance there’s so much pseudointellectual cachet going on here that I almost feel I’m cheapening it by telling anyone. Let’s just agree that if you read this article before Friday you can tell anyone you hear it from later that you liked it before it went mainstream. Mail me a postcard, I’ll send you the single when it comes out on vinyl.

That was a little florid, so let me cut to the chase, which is this: don’t use power bars with surge protectors for your personal computer. It’s fine to use them anywhere else, though you also want to avoid them for any attached external drives and their various connective tissues, USB hubs and network switches, for example. But your computer, at least, you want to be either plugged into a decent UPS or directly into the wall.

Almost all power bars but the very cheapest include surge protectors now, and if you’re trying to protect sensitive equipment you’d think you’d want something like that between your relatively delicate computer and the outside world. But protecting a computer from a surge by cutting the power is a lot like protecting someone from secondhand smoke by putting them in a chokehold. Strictly speaking your surge protector may be protecting your hardware, but in exchange for that you’re assuming a lot of risk involving your data.

Specifically, you’re accepting the risk of killing your box in the middle of an important write or, worse, with an unknown quantity of uncommitted data still in your drive’s onboard cache that’s just gone, never to be seen again. And on the off chance you’re (foolishly, in my opinion) using RAID at home the risk to your data actually gets worse, not better.

It’s harmless in the case of your appliances, game consoles or printers, and we all need more sockets than we have. But in terms of data preservation, if you don’t have a UPS you’re far better off plugging straight into the wall and letting your power supply take the abuse.

8 Comments | Skip to comment form

  1. John

    Okay, I’ll bite. Why is RAID at home foolish?

  2. Mike Kozlowski

    Because RAID is flaky, and there are far more ways a cheap consumer RAID 5 thing can fail unrecoverably than there are ways a single disk can fail.

  3. John

    But a single disk that fails has *failed* and requires restoring from backup.

    A RAID failure (which is more common than a single disk failure pretty much by definition – more disks to fail means mean time before first failure drops significantly) just requires a disk swap and a rebuid-while-working. It’s “swap some plugs and reboot”, instead of “real downtime”

  4. Mike Kozlowski

    No, many kinds of RAID failures destroy data. You can’t just pull a disk out of a RAID 5 array and read the data off it normally, right? It requires the RAID volume shit to work, and that’s what always gets corrupted with the cheap RAIDs.

  5. mhoye

    Raid is useful where a drive failure means somebody can deal with that while everyone else gets on with their work. At home, there is no “everyone else”. You need to deal with the problem immediately, which usually means “shut down, go out and buy a new drive immediately, bring it home and plug it in.” And it introduces many new ways outside just the disks that things can fail, including the dreaded but surprisingly common simultaneous drive failures due to shitty controllers or (in external enclosures) shitty power supplies.

    In short, it introduces far more failure-prone complexity than it offers in advantages. You still need backups, so just have backups.

  6. John

    You can’t just pull a disk out of a RAID 5 array and read the data off it normally, right?

    You can’t, but you *can* do that do a single drive in a RAID-1 array. Unless your RAID controller is especially stupid. Which is an argument against using stupid RAID, not against using RAID.

    At home, there is no “everyone else”. You need to deal with the problem immediately, which usually means “shut down, go out and buy a new drive immediately, bring it home and plug it in.”

    At which point, the system comes up and works normally while being slightly slow. As opposed to a single-disk failure, where the system needs to be reconfigured and restored from backup.

    And it introduces many new ways outside just the disks that things can fail, including the dreaded but surprisingly common simultaneous drive failures due to shitty controllers or (in external enclosures) shitty power supplies.

    This seems more to be an argument against using shitty controllers.

    And yeah, OF COURSE RAID doesn’t replace backups – but, done properly, it does reduce the incidence of needs to rebuild and restore from backup. Your arguments seem to be more about the folly of using *bad* RAID.

    Seriously, if the RAID controller blows shit up, you’re stuck restoring from backup, sure – but that’s the same as if a non-RAID hard drive fails. And if a single drive fails from your RAID, you get minimal downtime and no need to restore.

  7. John

    (As far as complexity goes: Absolutely, more complex. But much less annoying in case of the most common failure mode, and the ability to *not have to do my day job* when a disk fails at home is a source of anti-stress for me.)

  8. Ian Hurst

    I have been telling people for years not to bother with surge protectors, but nobody ever listens. And I really mean nobody… even I still have one under my desk. Following your own advice is for pussies.

    RAID5 at home is loony too. RAID1… maybe. But why not use a backup service instead? Unless uptime is critical – in which case wtf are you doing running your shit at home? – backup services are safer and simpler.