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Member
Teagan Tobias
Posts: 513

Cache size?

In V3 in Preferences under Setup, General, Cache:
what is a good cache size, is bigger better?

Peggy Paperdoll
Posts: 6,325
Registered: ‎12-30-2009

Re: Cache size?

Reply to Teagan Tobias - view message

There are two theories of thought on cache sizes.  One is that a small cache size is best because it takes less time to search the cache when your viewer calls for a texture or object (the viewer always checks the cache first before it dowloads from the server).  The smaller size does cause older cached items to be overwritten more often which means you will be downloading more from the servers once the cache is filled.  The other thought is a larger cache is best because more can be stored locally to make textures and objects quicker to rezz.  Your computer can pull a cached item up and rezz it much quicker that downloading it from the servers then rezzing it.  I fall about in the middle of those two lines to thinking.  An overly large cache can contain so many items that searching becomes a factor in the time to rezz.....especially if the item is not in the cache yet since the viewer will search the entire cache before it decides it needs to download from the servers.  And an extremely small cache can be searched quickly but fewer items can be cached which means more downloading from the servers......meaning slower rezz times.  There's also the added complication with small caches of files becoming corrupted because of the overwriting of older files (and that can lead to some significant problems that only a clearing of the cache will fix).

The default cache size of 500 megs is probably best........at least that's what I found.  No matter what size cache you set, it's best to move the cache to a separate drive.....especially if you are using a Windows machine.  The cache becomes heavily fragmented over time (and that can be a very short period of time too).  If the cache in on your operating system drive then that fragments your Windows which will slow you down a lot.

Member
Teagan Tobias
Posts: 513

Re: Cache size?

Reply to Peggy Paperdoll - view message

Thanks Peggy.  From the sounds of it the speed of the computer may play a part also.  I was going to go really big but think I will start around 1024 mg and see how it works.  Thanks again.

Advisor
Jenni Darkwatch
Posts: 1,622

Re: Cache size?

Reply to Teagan Tobias - view message

Peggys answer is entirely accurate. It might bear mentioning that different operating systems behave differently with large caches. Windows is about the worst, because of drive fragmentation. Mac is usually fine, unless the disk becomes near full. More or less same for Linux.

If you do have the money, you can use SSDs which might improve access time. However: SSDs still vary wildly in performance and reliability. Older models suffer from severe performance degradation over time. Newer ones not so much.

An alternative is to use a so-called "persistent RAM-Disk". The big disadvantage: You'll need a lot of memory for it. The big advantage: It's blazing fast.

Then there's the issue of what is being cached. If you hang out at the same places often, a cache can help a lot. On the other hand, if you hop around a lot and especially frequent busy venues, the benefit of any kind of cache is nearly imperceptible.

Member
Teagan Tobias
Posts: 513

Re: Cache size?

Reply to Jenni Darkwatch - view message

What you have said makes me somewhat hopeful of what I am going to try. My new Windows 7 computer has USB3 ports and I have ordered a 16G stick to use with ReadyBoost and/or try and use for my SL cache. It should be fast but if it will be as fast as a ram disk I don't know. Did not use fast mail so still a week away from getting here. Fingers crossed.

Posts: 3,022
Registered: ‎03-26-2009

Re: Cache size? Diff Opinion

[ Edited ]

Reply to Teagan Tobias - view message

I'm going to disagree with both of the other answers.

In 2011 a new caching system was added. The current cache is indexed. So, search time is minimal in ALL cases. Prior to the new cache a texture was searched for by the Operatng System by looking through the file system. Now it is a data query into a database index.

In the old cache a large cache took longer to find the needed file. A too small cache that filled up meant that the system had to find old files and delete them before attempting a download, which made things really slow. So, depending on the computer there was some balance point between the cache filling up and slowing for deletions and having too many files to look through. Experiementing was needed to find the optimum size on each computer.

Now 500mb is the minimum cache size.

For best performance some are placing their cache in a RAM or SSD drive. But, it has to be persistant or you are forver downloading files and running slower. Wherever you put the cache it will likely work best if it is on a drive other than the drive with the operating system's temp files and paging file.

Size is far less of an issue than it has ever been. But, if you use multiple viewers, i.e., Firestorm, project viewers, ... be sure they have separate caches. Any that share the cache should have the same size cache set. Allowing the main SL Viewer to have a large cache and a project viewer a small cache seems to slow the small cache viewer down. I have not tested that idea scientifically. It's just my impression.

Go for a larger cache. Watch the size of your caches. Regardless of what size I allowcate (1-10gb), the cache seems to run between 600k-700k.

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Kathmandu Gilman
Posts: 102

Re: Cache size?

Reply to Teagan Tobias - view message

Readyboost will not help much unless you are running with less than 2 gigs of system memory. Unless things have changed much in the last few years, thumbdrive memory is slow... Glacially slow compared to even a slow 5400rpm disk drive. They seem fast because you typically move small files with them. A 25meg per second transfer rate for a thumb drive is blazingly quick and only a few will go that fast. A hard drive typically does 70meg per second and a pair of Chronos SSDs in RAID0 will do 1000 megs per second sequential read and a Ramdrive will do 5000 megs per second or better. I've tried them all and really, the difference is imperceptible with a fast computer and a fast internet connection. 

On a fast, modern computer searching the cashe is quick. Even a 2 gig cashe can be searched in a fraction of a second because the computer is not looking through each file, it looks through a file table which is only a few megs at most. 10 years ago, when SL was still being developed, a 1 gig cashe could take a while to search through but with an Intel i7 CPU it takes less time to search than it takes for the enter key to pop back up after being pressed.

Member
Teagan Tobias
Posts: 513

Re: Cache size?

Reply to Kathmandu Gilman - view message

You have said a lot and I thank you for the input. But nothing about the newer USB3 that has a “theoretical maximum rate of 5Gbps”. USB 3.0 is also full duplex. I do not expect to see that speed but it should be interesting to see how it works if I can point my SL cache at it.

Advisor
Jenni Darkwatch
Posts: 1,622

Re: Cache size?

Reply to Teagan Tobias - view message

Realistic speeds for USB3 drives are between 75 and 100MB/sec sequential. Write is typically slower. For SL cache it matters more to have fast seek and fast random access. Should work well, actually.