David Schwartz

16,400 reputation

11338

bio	website
	location	Murphys, CA
	age	43
visits	member for	1 year, 9 months
	seen	2 days ago
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I am OpenCoin's Chief Cryptographer and one of the architects of the Ripple payment system.

I live in California's Gold Country, east of Sacramento.

Bitcoin: 1Gonhezk1ScHaFqUSYH9VQThaDS4PJSq1o

	16,400 reputation	bio	website		visits	member for	1 year, 9 months
11338 badges		location	Murphys, CA		seen	2 days ago

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Apr 9	comment	I think I'm under DoS attack. How can I respond? Have any of these IPs retrieved your `robots.txt` file? Does your `robots.txt` file prohibit these requests? What is the `Host` header in these requests? It could just be a legitimate spider following bad links or an old DNS entry from whatever had your IP address before you.
Apr 9	answered	Increase FD limitation then SSH not working?
Apr 8	comment	Trouble passing Trustwave PCI Scan due to BEAST vulnerability Is there any explanation available about what the vulnerability is? Are you not supposed to allow AES128? Are you not supposed to allow SHA?
Apr 8	comment	Send TCP/IP packets down three routes and pick fastest You should talk directly to someone with expertise in wide area networking. You will need several back and forth rounds of the expert asking questions and you giving answers to focus in on the right solution. To start, figure out what your requirements are and forget any notions you might have about how you think you will meet them. Details will matter. Is this bulk data? Lots of tiny bits. The occasional tiny bit? Is it requested by the client or unsolicited? Can you run your own "shim" on both ends? Is the same data going to all clients? And so on.
Apr 8	comment	Is it possible to set up a management VLAN on HP switches without configuring routes on the WAN routers? If you have layer 3 switches, they can usually do inter-VLAN routing.
Apr 8	comment	Changing Router IP Address/Default Gateway You should be able to run both simultaneously during the conversion process. As soon as the routers have at least one LAN in common and are sharing routing tables, either one should work fine as the default gateway for any network it's connected to. If a packet goes to the "wrong" router, it should just forward it to the other over the common LAN. You can also use a dedicated link between the two routers (if you have a spare Ethernet port) and just use that dedicated link for traffic that gets to the "wrong" router.
Apr 8	comment	Can't detect computers on network even though they are all connected to the same wifi If the network administrator has enabled client isolation (sometimes called "AP isolation") then clients cannot talk directly to each other.
Apr 6	revised	Changing Router IP Address/Default Gateway added 5 characters in body
Apr 5	comment	Is it possible to set up a management VLAN on HP switches without configuring routes on the WAN routers? How are the subnets communicating with each other? Is there some router than you control that does it? Does your switch do inter-VLAN routing? Is your ISP managing a router that routes between subnets?
Apr 5	answered	Changing Router IP Address/Default Gateway
Apr 5	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? @performanceuser: It's a matter of your definition of "working set". You can answer either "yes" or "no" if you want. The pages are in memory. They are somewhat recently accessed but not very recently accessed. They are rigged for a transition page fault if accessed by any process. You are welcome to consider them part of the working set (of processes that have mapped them) or not as you wish. Windows can count them towards some processes that have them mapped and not others depending on whether any working sets have been trimmed.
Apr 5	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? (If this is the explanation, they will be counted as transition faults.)
Apr 5	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? The definition of a soft page fault is a page fault that doesn't require slow I/O. None of the things you cite are "definition" of a soft page fault, they're just describing some of the circumstances under which a soft page fault can occur. Aging a page requires a soft page fault if the page hasn't been accessed recently. The page ager sets pages to trigger a page fault if it needs to know when they are accessed. (There is no conceivable way Windows 7 could age the working set without soft page faults. Think about it.)
Apr 5	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? You're missing that pages in the working set are aged. To age pages, you must know that they weren't accessed. To know that they weren't accessed, you must know that they were accessed. To know that they were accessed, there must be a fault. The only way to do this is to periodically arrange for access to pages in the working set to trigger a page fault.
Apr 5	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? let us continue this discussion in chat
Apr 5	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? That is also called a soft page fault. A "page fault" is a fault triggered by accessing a page. A "hard page fault" (or "major page fault") is a page fault that requires slow I/O (disk, network, etcetera). A "soft page fault" (or "minor page fault") is a page fault that does not.
Apr 5	revised	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? added 500 characters in body
Apr 5	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? What I'm talking about has little to do with whether a page is in the working set or not. It's about whether the process has recently accessed the page. In order to manage things like page eviction and working sets, the OS has to know which pages a process has recently accessed. To determine this, it periodically arranges it so that those accesses trigger a soft page fault. The fault handler marks the page accessed and changes it so that accesses won't trigger a soft page fault until later when it needs to know again. Removing pages from the working set is much later in the process.
Apr 5	comment	Is it possible to set up a management VLAN on HP switches without configuring routes on the WAN routers? You want three separate management VLANs? Do you want them to be able to communicate with each other? If so, something will have to route between the VLANs. (And likely, a VPN or tunnel will be needed between the locations to carry management traffic.)
Apr 5	answered	arp packet received larger than packet sent, why?