Re: [patch] document flash/RAID dangers

[Pavel Machek]

>>>> THESE devices have the property of potentially corrupting blocks being
>>>> written at the time of the power failure,
>>>
>>> this is true of all devices
>>
>> Actually I don't think so. I believe SATA disks do not corrupt even
>> the sector they are writing to -- they just have big enough
>> capacitors. And yes I believe ext3 depends on that.
>
> Pavel, no S-ATA drive has capacitors to hold up during a power failure 
> (or even enough power to destage their write cache). I know this from 
> direct, personal knowledge having built RAID boxes at EMC for years. In 
> fact, almost all RAID boxes require that the write cache be hardwired to 
> off when used in their arrays.

I never claimed they have enough power to flush entire cache -- read
the paragraph again. I do believe the disks have enough capacitors to
finish writing single sector, and I do believe ext3 depends on that.

									Pavel
-- 
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