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1Внутри HDD ЛоготипАппаратные дисковые и потребительского HDD проблемы

A couple of years ago I was lucky enough to have the opportunity to purchase a second hand hardware raid 5 карта (Areca 1220) по очень низкой цене. Since then I have used the card along with several sets of drives (originally 300gig, then 750gig and currently 1Tb) in a dedicated server PC as a large network file-store for the family’s music, фото, видео и резервные копии.


Before I obtained the hardware card I tried using software raid, but found the results very disappointing. Сервер имеет малую мощность, single core cpu which isn’t really up to the task of acting as a raid-5 engine. Хотя я слышал, много раз, что RAID не резервный, this is a case where only a cheap solution will do. RAID-5 offers protection from single drive failure, which is good enough for my purposes. The dedicated card offers an enormous performance advantage, but in practice this isn’t very important. The features it adds however are! Отель Areca карта предлагает Операционная система independent raid solution which counts for a lot. It also offers online capacity expansion and raid-level migration (так, например, Я мог бы обновить RAID-6). Both of these features are much less simple with cheaper solutions.

Так, вы можете подумать,, what’s the problem. Ответ: the lack of options from Hard Disk manufacturers

Ever since using the Areca card I have suffered from occasional drivefailures”. Upon powering off and on the drive reappears as fully functional. I then have to spend many hours rebuilding the array from degraded back to normal. After much searching I have diagnosed the problem, but am unable to properly solve it.

Hard Drive manufacturers provide a range of drives for different purposes. The typical drives most of us buy are consumer level drives. The manufacturers also offer enterprise-class drives designed for servers which have intensive use patterns and 24.7 Провел. These drives are often physically identical, but have undergone additional testing and are supplied with slightly different firmware, optimised for server workloads.

One of these features is Error Recovery Control (ERC). This feature is also called CCTL (Command Completion Time Limit) by Samsung and Hitachi and TLER (Time-Limited Error Recovery) by Western Digital. All drives suffer the occasional error at a physical level, which could be caused by things like stray cosmic rays. These errors are handled by redundancy built into the way the drive stores data, but occasionally one can be severe enough to cause problems reading data. Normal consumer drives will spend a prolonged period attempting to read the damaged data to recover it. They then map it to a new part of the drive and everything continues as normal. Однако, this delay can cause severe problems in enterprise environments, so enterprise drives will time-out their self-repair attempts after a short period (как правило 7 секунд или около) and report the error to the raid controller. The raid controller then handles the error by recalculating the data using the other drives in the array. This prevents large delays in sending data, but requires the presence of other drives and a raid controller.

Так, I have a proper hardware raid card. It expects to hear back from drives within no more than 7-8 seconds regardless of an error. I also have consumer hard drives, которые пытаются восстановить свои собственные ошибки в течение длительного периода. Поэтому, когда возникает ошибка привод пытается это исправить, doesn’t respond within 7-8 секунд, and the raid controller than assumes the drive has failed and kicks it out of the array.

Так, the obvious solutions would be either to tell the raid controller to wait longer without kicking a drive out, Или скажите диск сдаваться после 7 seconds like an enterprise driveInfuriatingly, ни можно!

I have searched extensively, но я не могу найти правильные RAID-5 карт, которые позволяют пользователю изменять как долго они будут ждать привода. In the past there were some WD drives which could have the TLER feature enabled with a utility released by WD called WD-TLER, but recently WD have disabled this option, presumably toprotectthe huge markup on their enterprise drives (которые удваивают цену за том же оборудовании)

Some people have found ways to temporarily enable ERC on some drives using either HDAT2, SmartCTL или Hdparm, however these do not support my RAID card under Windows, и изменение теряется, если ПК выключении и повторном включении.

For users like myself that need a large capacity storage, and the features offered by a hardware raid-5 solution, но это не нужно 24.7 Провел, long warranties or drives designed for heavy duty usage there is currently NO appropriate solution. Its about time either a drive manufacturer addressed this market (by releasing a consumer drive with ERC enabled for a small, например. 15%, премия) or a raid-card manufacturer addressed the market by offering a card with the option to increase the time before drives are timed out. Creating either of these solutions is trivial, a simple firmware tweak would do the job.

До тех пор, I advise others to avoid using hardware raid cards with consumer drives, and given the price premium of enterprise drives I recommending avoiding hardware raid altogether.

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