Re: [squid-users] Caching Video Content

As explained to me, the issue is that retrieving successive 4K blocks
of an object in memory takes non-linear amounts of CPU time - it takes
X cycles to retrieve the first 4K, but 2*X to retrieve the second 4K,
3*X to retrieve the third 4K, etc. etc.

-C

On May 24, 2009, at 12:19 PM, Dror Galron wrote:

> Thank you for your answers,
>
> I have not understood your statement of "Squid-2 has 4KB buffers to
> store objects, so the larger ones have some issues doing read seeks"
>
> Could you please emphasize on this?
>
> Thank you,
> Dror
>
>
> On Thu, May 21, 2009 at 6:26 AM, Amos Jeffries
> <squid3_at_treenet.co.nz> wrote:
>>> Hi,
>>>
>>> I am considering implementing Squid as my web cache for Video
>>> streams
>>> (YouTube etc).
>>> I am going to configure Squid over SAN centralized storage.
>>> I am aware of the additional plug-in required to "normalize" YouTube
>>> URL's.
>>> I have few questions:
>>> 1) Are there any example installations of Squid as Video oriented
>>> cache
>>> server?
>>
>> I'm not aware of anything published.
>>
>>> 2) If I implement Squid peering (either digest or ICAP), how does
>>
>> I think you mean: CARP.
>> ICAP is a filtering or adaptation method.
>>
>>> Squid solves "popular object" problem, when one cache within the
>>> cluster serves the most popular movie. As far as I understand, in
>>> this
>>> case all requests for that movie would be served from one particular
>>> server; this will cause overloading of that server.
>>
>> The versions of Squid-2 which have the storeurl features for
>> normalizing
>> you-tube requests also contain collapsed_forwarding which damps
>> this type
>> of overload down a lot. Squid efficiency rises enormously under
>> this type
>> of hot-object scenario up to close around 100% on the single
>> object. Note
>> this occurs at BOTH levels of the squid mesh, receiving and source
>> Squids
>> doing effective multicast for HTTP.
>>
>> This is one reason CDN people love Squid so much.
>>
>>
>>> 3) Are there any limitations / recommendations for maximal storage
>>> size that has many separate physical disks?
>>
>> No more than one cache_dir per disk. Squid can easily handle up to 63
>> cache_dir entries and thus disks. Beyond that certain types of RAID
>> do
>> actually start to be useful.
>>
>>
>>> 4) Are there any limitations regarding maximal cached object size?
>>>
>>
>> Squid-2 has 4KB buffers to store objects, so the larger ones have
>> some
>> issues doing read seeks. I forget what the limits were.
>>
>>
>> Amos
>>
>>
>>
>
>
>
> --
> Dror Galron
>
Received on Sun May 24 2009 - 19:34:38 MDT