"Leslie Rhorer" <lrhorer@xxxxxxxxxxx> writes:
>> > High enough? Wouldn't a higher speed limit mean more stress on the
>> systems?
>> > Its value is 1000.
>>
>> A higher min value will block more normal IO (if there is
>> any).
>
> No, not really. All the system that is currently being grown does
> is incrementally rsync the data from the main server every morning. The
> main server, which will be grown after this server is done, is another
> matter.
>
>> Raising min is usefull to ensure the job gets done in a certain
>> time, to not let normal IO slow down a rebuild too much.
>
> OK, but like I said, for the most part there isn't any other I/O.
>
>> >> MB/s) along with /proc/sys/dev/raid/speed_limit_max?
>> >
>> > It's 200,000
>>
>> I only ever had to tune this once when too much IO would deadlock an
>> external enclosure. Otherwise keep this really high so it uses all
>> idle IO there is.
>
> 200MBps is far more than the system can handle. These are consumer
> class drives on a relatively inexpensive 4 port controller feeding a Port
> Multiplier chassis.
>
>> As to your initial question: Being able to keep the filesystem mounted
>> and used is the whole point of having online growing of the raid
>> system. If that weren't save then there would be no point to it as you
>> could just as well stop the raid if you already umounted it and grow
>> it offline.
>
> I know that is the point of the utility. My question boils down to,
> "How safe is it to avail one's self of the capability if it is not essential
> to have the array mounted for the duration?" I don't particularly like
> having the array unavailable (especially not for nearly 5 days), but I
> prefer that to risking data loss, or especially risking irretrievably losing
> the entire array. The question is particularly pertinent given the fact the
> growth is going to take nearly 5 days (a lot can happen in 5 days), and the
> fact the system was having the rather squirrelly issue a few days back which
> seems - emphasis on SEEMS - to have been resolved by disabling NCQ. What
> happens if the system kicks a couple of drives, especially if one drive gets
> kicked, a bunch of data gets written and then a few minutes later another
> drive gets kicked? In particular, what if neither of the two drives that
> get kicked are the new drive?
It should just keep going. I don't see how having the filesystem in
use will have any influence there other than adding a little more load
on the disks. Reshaping is heavy on the drive. Lots of reads, writes
and seeks. A daily rsync probably doesn't even register as extra load.
MfG
Goswin
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