Compact Flash Web Proxy Reliability / Speed

Hardware MikroTik hardware general
1

Been reading up on the use of CF cards for web proxying, and I’m intrigued by this possibility.

My questions on the matter would be:

  1. Is this setup really reliable? If I have, say 200+ users on a branch site connected to a 100Mbit link, how long will it take before a typical, say, 8GB CF card will choke due to the repeated write cycles? Days, weeks, months, years? We’d only really be happy with the solution if the card ran for at least a year or two before finally cracking under the strain (similar to a HDD for example).

  2. What about the speed? We currently use small PCs with a Linux installation for this purpose; these boxes (in addition to being an administrative headache at times) are managing around 20-40Mbps overall. A Routerboard is capable of shunting well over this figure over two ethernet links under normal circumstances; how serious is the bottleneck when running proxy over CF?

  3. Is there any major difference with this configuration running with the RB600 vs the RB1000? (In other words, is the processor a serious bottleneck when running the web proxy in conjunction with some light routing/firewalling/NAT/port-forwarding, a bit of H323, a rarely-used management VPN and DNS caching/general networking stuff?

2

Actually, after reading some explanations here and running the figures through I can see how these devices would be reliable if the filesystem is correctly implemented.

A typical cache will only hold requests up to 4MB in size, so a 16GB CF card would hold at least 4000 of these. Assuming that the link is being absolutely hammered, this would be used up in perhaps 15 minutes or so (in practice you may not even get 4000 GETs in a day, but I’m thinking worst-case).

So that means that the card should be good for around 15*100,000 minutes assuming a perfect overwriting algorithm, or 3125 days assuming 8-hour work days. The overwriting will not be perfect, so cut this in half, that is still four years for a heavily-used card assuming that there is not a single sector that is being constantly overwritten. This I can live with, it’s on paper better than a standard HDD so no problems there.

Assuming that I’m basically right here, I’m happy to accept the principle as-read.

The only other question is performance: a typical 133x card should be able to outperform a 100Mbps link so no problems there, assuming that the Routerboards utilise MDMA for transfers – is this the case?

Thanks for any insights anyone has on this matter!