On Oct 16, 2011, at 3:56 AM, Jim Klimov wrote:

> 2011-09-29 17:15, Zaeem Arshad пишет:
>> On Thu, Sep 29, 2011 at 11:33 AM, Garrett D'Amore <garrett.dam...@gmail.com> 
>> wrote:
>> I think he means, resilver faster.
>> SSDs can be driven harder, and have more IOPs so we can hit them harder with 
>> less impact on the overall performance.  The reason we throttle at all is to 
>> avoid saturating the bandwidth of the drive with resilver which would 
>> prevent regular operations from making progress.  Generally I believe 
>> resilver operations are not "bandwidth bound" in the sense of pure 
>> throughput, but are IOPs bound.  As SSDs have no seek time, they can handle 
>> a lot more of these little operations than a regular hard disk.
>>  - Garrett
>> What's the throttling rate if I may call it that?
> IIRC about 7MBps, and I guess it is hardcoded since the value 
> is so well known as to have been reported several times.

No, the resilver throttling is more based on IOPS than bandwidth.

> I think another rationale for SSD throttling was with L2ARC tasks -
> to reduce probable effects of write overdriving in SSD hardwares
> (less efficient and more wear on SSD cells).

L2ARC fill rate is, by default in most distros, 16MB/sec until full, then 
 -- richard


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