On Thu, Feb 25, 2010 at 5:19 PM, Denys Fedorysychenko
<nuclearcat@xxxxxxxxxxxxxx> wrote:
> On Thursday 25 February 2010 13:42:52 Amos Jeffries wrote:
>> My opinion of RAID behind Squid is very poor. Avoid if at all possible.
>>
>> HW RAID is claimed to be workable though, particularly as the price
>> range and quality goes up.
>>
>> The RAID0 operations of striping are duplication of the object spread
>> Squid itself performs between its cache_dir. So all you really gain
>> there is a larger total disk (Squid don't care about that) and risk of
>> loosing the entire lot if any stripe platters die.
> What about that sequental read of file on RAID0 is faster?
> Sure if file is larger than double stripe size.
There's pros and cons. Squid reads data in in small chunks; RAID0 has
the pro of being able to parallelize reads across spindles, but then
often has the disadvantage of reading in a whole stripe when accessing
a block; This most likely means that squid's access patterns trash the
RAID controller's cache.
In other words, if you can please go JBOD and let Squid balance across
disks. It's simply a safer choice to get performance. In case of HDD
failure cache data are by definition easilty re-imported (it would be
nice if squid was more graceful in handling disk failures, but
still..)
--
/kinkie
