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  • APC PHP cache size does not exceed 32MB, even though settings allow for more

    - by hardy101
    I am setting up APC (v 3.1.9) on a high-traffic WordPress installation on CentOS 6.0 64 bit. I have figured out many of the quirks with APC, but something is still not quite right. No matter what settings I change, APC never actually caches more than 32MB. I'm trying to bump it up to 256 MB. 32MB is a default amount for apc.shm_size, so I am wondering if it's stuck there somehow. I have run the following echo '2147483648' > /proc/sys/kernel/shmmax to increase my system's shared memory to 2G (half of my 4G box). Then ran ipcs -lm which returns ------ Shared Memory Limits -------- max number of segments = 4096 max seg size (kbytes) = 2097152 max total shared memory (kbytes) = 8388608 min seg size (bytes) = 1 Also made a change in /etc/sysctl.conf then ran sysctl -p to make the settings stick on the server. Rebooted, too, for good measure. In my APC settings, I have mmap enabled (which happens by default in recent versions of APC). php.ini looks like: apc.stat=0 apc.shm_size="256M" apc.max_file_size="10M" apc.mmap_file_mask="/tmp/apc.XXXXXX" apc.ttl="7200" I am aware that mmap mode will ignore references to apc.shm_segments, so I have left it out with default 1. phpinfo() indicates the following about APC: Version 3.1.9 APC Debugging Disabled MMAP Support Enabled MMAP File Mask /tmp/apc.bPS7rB Locking type pthread mutex Locks Serialization Support php Revision $Revision: 308812 $ Build Date Oct 11 2011 22:55:02 Directive Local Value apc.cache_by_default On apc.canonicalize O apc.coredump_unmap Off apc.enable_cli Off apc.enabled On On apc.file_md5 Off apc.file_update_protection 2 apc.filters no value apc.gc_ttl 3600 apc.include_once_override Off apc.lazy_classes Off apc.lazy_functions Off apc.max_file_size 10M apc.mmap_file_mask /tmp/apc.bPS7rB apc.num_files_hint 1000 apc.preload_path no value apc.report_autofilter Off apc.rfc1867 Off apc.rfc1867_freq 0 apc.rfc1867_name APC_UPLOAD_PROGRESS apc.rfc1867_prefix upload_ apc.rfc1867_ttl 3600 apc.serializer default apc.shm_segments 1 apc.shm_size 256M apc.slam_defense On apc.stat Off apc.stat_ctime Off apc.ttl 7200 apc.use_request_time On apc.user_entries_hint 4096 apc.user_ttl 0 apc.write_lock On apc.php reveals the following graph, no matter how long the server runs (cache size fluctuates and hovers at just under 32MB. See image http://i.stack.imgur.com/2bwMa.png You can see that the cache is trying to allocate 256MB, but the brown piece of the pie keeps getting recycled at 32MB. This is confirmed as refreshing the apc.php page shows cached file counts that move up and down (implying that the cache is not holding onto all of its files). Does anyone have an idea of how to get APC to use more than 32 MB for its cache size?? **Note that the identical behavior occurs for eaccelerator, xcache, and APC. I read here: http://www.litespeedtech.com/support/forum/archive/index.php/t-5072.html that suEXEC could cause this problem.

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  • CPU fan making noise. plz suggest

    - by user32185
    CPU fan is making noise ...i figured out reasons: Cable coming out of fan is vibrating ... And may be also CPU fan is loose causing vibration... suggest options... i cleaned the fan ...but found that there is no heatsink compound /paste between processor and the fan..is it ok . My processor is p4 2.4 ghz motherboard intel 845 gvsr

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  • What is the CPU microcode?

    - by golem
    Today after unpacking the initramfs file from my Linux /boot directory I found that it contains the GenuineIntel.bin file, and that that file is an image of what is called the CPU microcode. Then I found articles on ArchWiki and Wikipedia describing the subject. Now I'm not sure that my vague understanding of the subject is correct. Can anyone please explain what the CPU microcode is in plain English?

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  • How can I find a list of all SSE instructions? What happens if a CPU doesn't support SSE?

    - by Blastcore
    So I've been reading about how processors work. Now I'm on the instructions (SSE, SSE2, etc) stuff. (Which is pretty interesting). I have lot of questions (I've been reading this stuff on Wikipedia): I've saw the names of some instructions that were added on SSE, however there's no explanation about any of them (Maybe SSE4? They're not even listed on Wikipedia). Where can I read about what they do? How do I know which of these instructions are being used? If we do know which are being used, let's say I'm doing a comparison, (This may be the most stupid question I've ever asked, I don't know about assembly, though) Is it possible to directly use the instruction on an assembly code? (I've been looking at this: http://asm.inightmare.org/opcodelst/index.php?op=CMP) How does the processor interpret the instructions? What would happen if I had a processor without any of the SSE instructions? (I suppose in the case we want to do a comparison, we wouldn't be able to, right?)

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  • SQL SERVER – Service Broker and CAP_CPU_PERCENT – Limiting SQL Server Instances to CPU Usage

    - by pinaldave
    I have mentioned several times on this blog that the best part of blogging is the questions I receive from readers. They are often very interesting. The questions from readers give me a good idea what other readers might be thinking as well. After reading my earlier article Simple Example to Configure Resource Governor – Introduction to Resource Governor – I received an email from a reader and we exchanged a few emails. After exchanging emails we both figured out what is going on. It was indeed interesting and reader suggested to that I should blog about it.  I asked for permission to publish his name but he does not like the attention so we will just call him Jeff. I have converted our emails into chat for easy consumption. Jeff: Your script does not work at all. I think either there is a bug in SQL Server. Pinal: Would you please explain in detail? Jeff: Your code does not limit the CPU usage? Pinal: How did you measure it? Jeff: Well, we have third party tools for it but let us say I have limited the resources for Reporting Services and used your script described in your blog. After that I ran only reporting service workload the CPU is still used more than 100% and it is not limited to 30% as described in your script. Clearly something is wrong somewhere. Pinal: Did you say you ONLY ran reporting server load? Jeff: Yeah, to validate I ran ONLY reporting server load and CPU did not throttle at 30% as per your script. Pinal: Oh! I get it here is the answer - CAP_CPU_PERCENT = 30. Use it. Jeff: What is that, I think your earlier script says it will throttle the Reporting Service workload and Application/OLTP workload and balance it. Pinal: Exactly, that is correct. Jeff: You need to write more in email buddy! Just like your blogs, your answers do not make sense! No Offense! Pinal: Hmm…feedback well taken. Let me try again. In SQL Server 2012 there are a few enhancements with regards to SQL Server Resource Governor. One of the enhancement is how the resources are allocated. Let me explain you with examples. Configuration: [Read Earlier Post] Reporting Workload: MIN_CPU_PERCENT=0, MAX_CPU_PERCENT=30 Application/OLTP Workload: MIN_CPU_PERCENT=50, MAX_CPU_PERCENT=100 Example 1: If there is only Reporting Workload on the server: SQL Server will not limit usage of CPU to only 30% workload but SQL Server instance will use all available CPU (if needed). In another word in this scenario it will use more than 30% CPU. Example 2: If there is Reproting Workload and heavy Application/OLTP workload: SQL Server will allocate a maximum of 30% CPU resources to Reporting Workload and allocate remaining resources to heavy application/OLTP workload. The reason for this enhancement is for better utilization of the resources. Let us think, if there is only single workload, which we have limited to max CPU usage to 30%. The other unused available CPU resources is now wasted. In this situation SQL Server allows the workload to use more than 30% resources leading to overall improved/optimized performance. However, in the case of multiple workload where lots of resources are needed the limits specified in MAX_CPU_PERCENT are acknowledged. Example 3: If there is a situation where the max CPU workload has to be enforced: This is a very interesting scenario, in the case when the max CPU workload has to be enforced irrespective of the workload and enhanced algorithm, the keyword CAP_CPU_PERCENT is essential. It specifies a hard cap on the CPU bandwidth that all requests in the resource pool will receive. It will never let CPU usage for reporting workload to go over 30% in our case. You can use the key word as follows: -- Creating Resource Pool for Report Server CREATE RESOURCE POOL ReportServerPool WITH ( MIN_CPU_PERCENT=0, MAX_CPU_PERCENT=30, CAP_CPU_PERCENT=40, MIN_MEMORY_PERCENT=0, MAX_MEMORY_PERCENT=30) GO Notice that there is MAX_CPU_PERCENT=30 and CAP_CPU_PERCENT=40, what it means is that when SQL Server Instance is under heavy load under different workload it will use the maximum CPU at 30%. However, when the SQL Server instance is not under workload it will go over the 30% limit. However, as CAP_CPU_PERCENT is set to 40, it will not go over 40% in any case by limiting the usage of CPU. CAP_CPU_PERCENT puts a hard limit on the resources usage by workload. Jeff: Nice Pinal, you should blog about it. [A day passes by] Pinal: Jeff, it is done! Click here to read it. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Service Broker

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  • video and file caching with squid lusca?

    - by moon
    hello all i have configured squid lusca on ubuntu 11.04 version and also configured the video caching but the problem is the squid cannot configure the video more than 2 min long and the file of size upto 5.xx mbs only. here is my config please guide me how can i cache the long videos and files with squid: > # PORT and Transparent Option http_port 8080 transparent server_http11 on icp_port 0 > > # Cache Directory , modify it according to your system. > # but first create directory in root by mkdir /cache1 > # and then issue this command chown proxy:proxy /cache1 > # [for ubuntu user is proxy, in Fedora user is SQUID] > # I have set 500 MB for caching reserved just for caching , > # adjust it according to your need. > # My recommendation is to have one cache_dir per drive. zzz > > #store_dir_select_algorithm round-robin cache_dir aufs /cache1 500 16 256 cache_replacement_policy heap LFUDA memory_replacement_policy heap > LFUDA > > # If you want to enable DATE time n SQUID Logs,use following emulate_httpd_log on logformat squid %tl %6tr %>a %Ss/%03Hs %<st %rm > %ru %un %Sh/%<A %mt log_fqdn off > > # How much days to keep users access web logs > # You need to rotate your log files with a cron job. For example: > # 0 0 * * * /usr/local/squid/bin/squid -k rotate logfile_rotate 14 debug_options ALL,1 cache_access_log /var/log/squid/access.log > cache_log /var/log/squid/cache.log cache_store_log > /var/log/squid/store.log > > #I used DNSAMSQ service for fast dns resolving > #so install by using "apt-get install dnsmasq" first dns_nameservers 127.0.0.1 101.11.11.5 ftp_user anonymous@ ftp_list_width 32 ftp_passive on ftp_sanitycheck on > > #ACL Section acl all src 0.0.0.0/0.0.0.0 acl manager proto cache_object acl localhost src 127.0.0.1/255.255.255.255 acl > to_localhost dst 127.0.0.0/8 acl SSL_ports port 443 563 # https, snews > acl SSL_ports port 873 # rsync acl Safe_ports port 80 # http acl > Safe_ports port 21 # ftp acl Safe_ports port 443 563 # https, snews > acl Safe_ports port 70 # gopher acl Safe_ports port 210 # wais acl > Safe_ports port 1025-65535 # unregistered ports acl Safe_ports port > 280 # http-mgmt acl Safe_ports port 488 # gss-http acl Safe_ports port > 591 # filemaker acl Safe_ports port 777 # multiling http acl > Safe_ports port 631 # cups acl Safe_ports port 873 # rsync acl > Safe_ports port 901 # SWAT acl purge method PURGE acl CONNECT method > CONNECT http_access allow manager localhost http_access deny manager > http_access allow purge localhost http_access deny purge http_access > deny !Safe_ports http_access deny CONNECT !SSL_ports http_access allow > localhost http_access allow all http_reply_access allow all icp_access > allow all > > #========================== > # Administrative Parameters > #========================== > > # I used UBUNTU so user is proxy, in FEDORA you may use use squid cache_effective_user proxy cache_effective_group proxy cache_mgr > [email protected] visible_hostname proxy.aacable.net unique_hostname > [email protected] > > #============= > # ACCELERATOR > #============= half_closed_clients off quick_abort_min 0 KB quick_abort_max 0 KB vary_ignore_expire on reload_into_ims on log_fqdn > off memory_pools off > > # If you want to hide your proxy machine from being detected at various site use following via off > > #============================================ > # OPTIONS WHICH AFFECT THE CACHE SIZE / zaib > #============================================ > # If you have 4GB memory in Squid box, we will use formula of 1/3 > # You can adjust it according to your need. IF squid is taking too much of RAM > # Then decrease it to 128 MB or even less. > > cache_mem 256 MB minimum_object_size 512 bytes maximum_object_size 500 > MB maximum_object_size_in_memory 128 KB > > #============================================================$ > # SNMP , if you want to generate graphs for SQUID via MRTG > #============================================================$ > #acl snmppublic snmp_community gl > #snmp_port 3401 > #snmp_access allow snmppublic all > #snmp_access allow all > > #============================================================ > # ZPH , To enable cache content to be delivered at full lan speed, > # To bypass the queue at MT. > #============================================================ tcp_outgoing_tos 0x30 all zph_mode tos zph_local 0x30 zph_parent 0 > zph_option 136 > > # Caching Youtube acl videocache_allow_url url_regex -i \.youtube\.com\/get_video\? acl videocache_allow_url url_regex -i > \.youtube\.com\/videoplayback \.youtube\.com\/videoplay > \.youtube\.com\/get_video\? acl videocache_allow_url url_regex -i > \.youtube\.[a-z][a-z]\/videoplayback \.youtube\.[a-z][a-z]\/videoplay > \.youtube\.[a-z][a-z]\/get_video\? acl videocache_allow_url url_regex > -i \.googlevideo\.com\/videoplayback \.googlevideo\.com\/videoplay \.googlevideo\.com\/get_video\? acl videocache_allow_url url_regex -i > \.google\.com\/videoplayback \.google\.com\/videoplay > \.google\.com\/get_video\? acl videocache_allow_url url_regex -i > \.google\.[a-z][a-z]\/videoplayback \.google\.[a-z][a-z]\/videoplay > \.google\.[a-z][a-z]\/get_video\? acl videocache_allow_url url_regex > -i proxy[a-z0-9\-][a-z0-9][a-z0-9][a-z0-9]?\.dailymotion\.com\/ acl videocache_allow_url url_regex -i vid\.akm\.dailymotion\.com\/ acl > videocache_allow_url url_regex -i > [a-z0-9][0-9a-z][0-9a-z]?[0-9a-z]?[0-9a-z]?\.xtube\.com\/(.*)flv acl > videocache_allow_url url_regex -i \.vimeo\.com\/(.*)\.(flv|mp4) acl > videocache_allow_url url_regex -i > va\.wrzuta\.pl\/wa[0-9][0-9][0-9][0-9]? acl videocache_allow_url > url_regex -i \.youporn\.com\/(.*)\.flv acl videocache_allow_url > url_regex -i \.msn\.com\.edgesuite\.net\/(.*)\.flv acl > videocache_allow_url url_regex -i \.tube8\.com\/(.*)\.(flv|3gp) acl > videocache_allow_url url_regex -i \.mais\.uol\.com\.br\/(.*)\.flv acl > videocache_allow_url url_regex -i > \.blip\.tv\/(.*)\.(flv|avi|mov|mp3|m4v|mp4|wmv|rm|ram|m4v) acl > videocache_allow_url url_regex -i > \.apniisp\.com\/(.*)\.(flv|avi|mov|mp3|m4v|mp4|wmv|rm|ram|m4v) acl > videocache_allow_url url_regex -i \.break\.com\/(.*)\.(flv|mp4) acl > videocache_allow_url url_regex -i redtube\.com\/(.*)\.flv acl > videocache_allow_dom dstdomain .mccont.com .metacafe.com > .cdn.dailymotion.com acl videocache_deny_dom dstdomain > .download.youporn.com .static.blip.tv acl dontrewrite url_regex > redbot\.org \.php acl getmethod method GET > > storeurl_access deny dontrewrite storeurl_access deny !getmethod > storeurl_access deny videocache_deny_dom storeurl_access allow > videocache_allow_url storeurl_access allow videocache_allow_dom > storeurl_access deny all > > storeurl_rewrite_program /etc/squid/storeurl.pl > storeurl_rewrite_children 7 storeurl_rewrite_concurrency 10 > > acl store_rewrite_list urlpath_regex -i > \/(get_video\?|videodownload\?|videoplayback.*id) acl > store_rewrite_list urlpath_regex -i \.flv$ \.mp3$ \.mp4$ \.swf$ \ > storeurl_access allow store_rewrite_list storeurl_access deny all > > refresh_pattern -i \.flv$ 10080 80% 10080 override-expire > override-lastmod reload-into-ims ignore-reload ignore-no-cache > ignore-private ignore-auth refresh_pattern -i \.mp3$ 10080 80% 10080 > override-expire override-lastmod reload-into-ims ignore-reload > ignore-no-cache ignore-private ignore-auth refresh_pattern -i \.mp4$ > 10080 80% 10080 override-expire override-lastmod reload-into-ims > ignore-reload ignore-no-cache ignore-private ignore-auth > refresh_pattern -i \.swf$ 10080 80% 10080 override-expire > override-lastmod reload-into-ims ignore-reload ignore-no-cache > ignore-private ignore-auth refresh_pattern -i \.gif$ 10080 80% 10080 > override-expire override-lastmod reload-into-ims ignore-reload > ignore-no-cache ignore-private ignore-auth refresh_pattern -i \.jpg$ > 10080 80% 10080 override-expire override-lastmod reload-into-ims > ignore-reload ignore-no-cache ignore-private ignore-auth > refresh_pattern -i \.jpeg$ 10080 80% 10080 override-expire > override-lastmod reload-into-ims ignore-reload ignore-no-cache > ignore-private ignore-auth refresh_pattern -i \.exe$ 10080 80% 10080 > override-expire override-lastmod reload-into-ims ignore-reload > ignore-no-cache ignore-private ignore-auth > > # 1 year = 525600 mins, 1 month = 10080 mins, 1 day = 1440 refresh_pattern (get_video\?|videoplayback\?|videodownload\?|\.flv?) > 10080 80% 10080 ignore-no-cache ignore-private override-expire > override-lastmod reload-into-ims refresh_pattern > (get_video\?|videoplayback\?id|videoplayback.*id|videodownload\?|\.flv?) > 10080 80% 10080 ignore-no-cache ignore-private override-expire > override-lastmod reload-into-ims refresh_pattern \.(ico|video-stats) > 10080 80% 10080 override-expire ignore-reload ignore-no-cache > ignore-private ignore-auth override-lastmod negative-ttl=10080 > refresh_pattern \.etology\? 10080 > 80% 10080 override-expire ignore-reload ignore-no-cache > refresh_pattern galleries\.video(\?|sz) 10080 > 80% 10080 override-expire ignore-reload ignore-no-cache > refresh_pattern brazzers\? 10080 > 80% 10080 override-expire ignore-reload ignore-no-cache > refresh_pattern \.adtology\? 10080 > 80% 10080 override-expire ignore-reload ignore-no-cache > refresh_pattern > ^.*(utm\.gif|ads\?|rmxads\.com|ad\.z5x\.net|bh\.contextweb\.com|bstats\.adbrite\.com|a1\.interclick\.com|ad\.trafficmp\.com|ads\.cubics\.com|ad\.xtendmedia\.com|\.googlesyndication\.com|advertising\.com|yieldmanager|game-advertising\.com|pixel\.quantserve\.com|adperium\.com|doubleclick\.net|adserving\.cpxinteractive\.com|syndication\.com|media.fastclick.net).* > 10080 20% 10080 ignore-no-cache ignore-private override-expire > ignore-reload ignore-auth negative-ttl=40320 max-stale=10 > refresh_pattern ^.*safebrowsing.*google 10080 80% 10080 > override-expire ignore-reload ignore-no-cache ignore-private > ignore-auth negative-ttl=10080 refresh_pattern > ^http://((cbk|mt|khm|mlt)[0-9]?)\.google\.co(m|\.uk) 10080 80% > 10080 override-expire ignore-reload ignore-private negative-ttl=10080 > refresh_pattern ytimg\.com.*\.jpg > 10080 80% 10080 override-expire ignore-reload refresh_pattern > images\.friendster\.com.*\.(png|gif) 10080 80% > 10080 override-expire ignore-reload refresh_pattern garena\.com > 10080 80% 10080 override-expire reload-into-ims refresh_pattern > photobucket.*\.(jp(e?g|e|2)|tiff?|bmp|gif|png) 10080 80% > 10080 override-expire ignore-reload refresh_pattern > vid\.akm\.dailymotion\.com.*\.on2\? 10080 80% > 10080 ignore-no-cache override-expire override-lastmod refresh_pattern > mediafire.com\/images.*\.(jp(e?g|e|2)|tiff?|bmp|gif|png) 10080 80% > 10080 reload-into-ims override-expire ignore-private refresh_pattern > ^http:\/\/images|pics|thumbs[0-9]\. 10080 80% > 10080 reload-into-ims ignore-no-cache ignore-reload override-expire > refresh_pattern ^http:\/\/www.onemanga.com.*\/ > 10080 80% 10080 reload-into-ims ignore-no-cache ignore-reload > override-expire refresh_pattern > ^http://v\.okezone\.com/get_video\/([a-zA-Z0-9]) 10080 80% 10080 > override-expire ignore-reload ignore-no-cache ignore-private > ignore-auth override-lastmod negative-ttl=10080 > > #images facebook refresh_pattern -i \.facebook.com.*\.(jpg|png|gif) 10080 80% 10080 ignore-reload override-expire ignore-no-cache > refresh_pattern -i \.fbcdn.net.*\.(jpg|gif|png|swf|mp3) > 10080 80% 10080 ignore-reload override-expire ignore-no-cache > refresh_pattern static\.ak\.fbcdn\.net*\.(jpg|gif|png) > 10080 80% 10080 ignore-reload override-expire ignore-no-cache > refresh_pattern ^http:\/\/profile\.ak\.fbcdn.net*\.(jpg|gif|png) > 10080 80% 10080 ignore-reload override-expire ignore-no-cache > > #All File refresh_pattern -i \.(3gp|7z|ace|asx|bin|deb|divx|dvr-ms|ram|rpm|exe|inc|cab|qt) > 10080 80% 10080 ignore-no-cache override-expire override-lastmod > reload-into-ims refresh_pattern -i > \.(rar|jar|gz|tgz|bz2|iso|m1v|m2(v|p)|mo(d|v)|arj|lha|lzh|zip|tar) > 10080 80% 10080 ignore-no-cache override-expire override-lastmod > reload-into-ims refresh_pattern -i > \.(jp(e?g|e|2)|gif|pn[pg]|bm?|tiff?|ico|swf|dat|ad|txt|dll) > 10080 80% 10080 ignore-no-cache override-expire override-lastmod > reload-into-ims refresh_pattern -i > \.(avi|ac4|mp(e?g|a|e|1|2|3|4)|mk(a|v)|ms(i|u|p)|og(x|v|a|g)|rm|r(a|p)m|snd|vob) > 10080 80% 10080 ignore-no-cache override-expire override-lastmod > reload-into-ims refresh_pattern -i > \.(pp(t?x)|s|t)|pdf|rtf|wax|wm(a|v)|wmx|wpl|cb(r|z|t)|xl(s?x)|do(c?x)|flv|x-flv) > 10080 80% 10080 ignore-no-cache override-expire override-lastmod > reload-into-ims > > refresh_pattern -i (/cgi-bin/|\?) 0 0% 0 refresh_pattern ^gopher: > 1440 0% 1440 refresh_pattern ^ftp: 10080 95% 10080 > override-lastmod reload-into-ims refresh_pattern . 1440 > 95% 10080 override-lastmod reload-into-ims

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  • SQL Server IO handling mechanism can be severely affected by high CPU usage

    - by sqlworkshops
    Are you using SSD or SAN / NAS based storage solution and sporadically observe SQL Server experiencing high IO wait times or from time to time your DAS / HDD becomes very slow according to SQL Server statistics? Read on… I need your help to up vote my connect item – https://connect.microsoft.com/SQLServer/feedback/details/744650/sql-server-io-handling-mechanism-can-be-severely-affected-by-high-cpu-usage. Instead of taking few seconds, queries could take minutes/hours to complete when CPU is busy.In SQL Server when a query / request needs to read data that is not in data cache or when the request has to write to disk, like transaction log records, the request / task will queue up the IO operation and wait for it to complete (task in suspended state, this wait time is the resource wait time). When the IO operation is complete, the task will be queued to run on the CPU. If the CPU is busy executing other tasks, this task will wait (task in runnable state) until other tasks in the queue either complete or get suspended due to waits or exhaust their quantum of 4ms (this is the signal wait time, which along with resource wait time will increase the overall wait time). When the CPU becomes free, the task will finally be run on the CPU (task in running state).The signal wait time can be up to 4ms per runnable task, this is by design. So if a CPU has 5 runnable tasks in the queue, then this query after the resource becomes available might wait up to a maximum of 5 X 4ms = 20ms in the runnable state (normally less as other tasks might not use the full quantum).In case the CPU usage is high, let’s say many CPU intensive queries are running on the instance, there is a possibility that the IO operations that are completed at the Hardware and Operating System level are not yet processed by SQL Server, keeping the task in the resource wait state for longer than necessary. In case of an SSD, the IO operation might even complete in less than a millisecond, but it might take SQL Server 100s of milliseconds, for instance, to process the completed IO operation. For example, let’s say you have a user inserting 500 rows in individual transactions. When the transaction log is on an SSD or battery backed up controller that has write cache enabled, all of these inserts will complete in 100 to 200ms. With a CPU intensive parallel query executing across all CPU cores, the same inserts might take minutes to complete. WRITELOG wait time will be very high in this case (both under sys.dm_io_virtual_file_stats and sys.dm_os_wait_stats). In addition you will notice a large number of WAITELOG waits since log records are written by LOG WRITER and hence very high signal_wait_time_ms leading to more query delays. However, Performance Monitor Counter, PhysicalDisk, Avg. Disk sec/Write will report very low latency times.Such delayed IO handling also occurs to read operations with artificially very high PAGEIOLATCH_SH wait time (with number of PAGEIOLATCH_SH waits remaining the same). This problem will manifest more and more as customers start using SSD based storage for SQL Server, since they drive the CPU usage to the limits with faster IOs. We have a few workarounds for specific scenarios, but we think Microsoft should resolve this issue at the product level. We have a connect item open – https://connect.microsoft.com/SQLServer/feedback/details/744650/sql-server-io-handling-mechanism-can-be-severely-affected-by-high-cpu-usage - (with example scripts) to reproduce this behavior, please up vote the item so the issue will be addressed by the SQL Server product team soon.Thanks for your help and best regards,Ramesh MeyyappanHome: www.sqlworkshops.comLinkedIn: http://at.linkedin.com/in/rmeyyappan

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  • [Java] Cluster Shared Cache

    - by GuiSim
    Hi everyone. I am searching for a java framework that would allow me to share a cache between multiple JVMs. What I would need is something like Hazelcast but without the "distributed" part. I want to be able to add an item in the cache and have it automatically synced to the other "group member" cache. If possible, I'd like the cache to be sync'd via a reliable multicast (or something similar). I've looked at Shoal but sadly the "Distributed State Cache" seems like an insufficient implementation for my needs. I've looked at JBoss Cache but it seems a little overkill for what I need to do. I've looked at JGroups, which seems to be the most promising tool for what I need to do. Does anyone have experiences with JGroups ? Preferably if it was used as a shared cache ? Any other suggestions ? Thanks ! EDIT : We're starting tests to help us decide between Hazelcast and Infinispan, I'll accept an answer soon. EDIT : Due to a sudden requirements changes, we don't need a distributed map anymore. We'll be using JGroups for a low level signaling framework. Thanks everyone for you help.

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  • Distributed Cache with Serialized File as DataStore in Oracle Coherence

    - by user226295
    Weired but I am investigating the Oracle Coherence as a substitue for distribute cache. My primarr problem is that we dont have distribituted cache as such as of now in our app. Thats my major concern. And thats what I want to implement. So, lets say if I take up a machine and start a new (3rd) reading process, it will be able to connect to the cache and listen to the cache and will have a full set of cache triplicated (as of now its duplicated) Now thats waste from a common person stanpoint too. The size of the cache is 2 GB and without going distibuted its limiting us. Thats bring me to Coheremce. But now, we dont have database as persistent store too. we have the archival processes as our persistent store. (90 days worth of data) Ok now multiply that with soem where around 2 GB * 90 (thats the bare minimum we want to keep). Preliminary/Intermediate analysis of Coherence as a solution. And a (supposedly) brilliant thought crossed my mind. Why not have this as persistant storage with my distributed cache. Does Oracle Coherence support that. I will get rid of archiving infrastructure too (i hate daemon archiving processes). For some starnge reasons, I dont wanna go to the DB to replace those flat files. What say?, can Coherence be my savior? Any other stable alternate too. (Coherence is imposed on me by big guys, FYI)

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  • Can I have damaged a CPU ?

    - by Pascal
    Hey guys, This is a question I asked on Anantech forums, but I just discovered this community and think this question would fit right in. Here goes: I built a PC around a Q9550 1 1/2 years ago (MoBo is an Asus P5Q deluxe). Specs give 2.83GHz, OC'ed it to 3.40 GHZ without any problem (or so I thought) till 2 months ago. Cooling is provided by stock Intel Fan... 2 Months ago, I began to see random crashes, bios saying CPU overheat error... PC would reboot at OC'ed speed without any problem. Since last saturday and a few more crashes, PC won't reboot at 3.40 GHz, and even at stock speed (2.83 GHz), I got core temperatures of (60 C idle, 95 C under load) on the first two cores. This is the 4 core temperatures I am talking about, not the T-CPU which obvioulsy is lower. Fan is running at a steady 2000 RPM. Questions for you : 1. Is 2000 RPM the normal speed of the Intel fan or is my fan somehow broken (which could explain the overheating). In this case, any recommendation for a good fan for OCing ? 2. Hypothesis I fear is the right one: can the CPU have been slowly damaged over time by this OCing, meaning there is nothing much to do except waiting for it to die ? (As a side note, I am surprised that the 9550 is still around 300 $CDN here... Thought it would have been cheaper with all those i3/i5/i7 around). Any help or advice would be more than welcome...

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  • Coffee spilled and went inside CPU...computer not starting

    - by Harpreet
    Today coffee got spilled over my table, and some of it (very less) reached the CPU placed under the table. I think little bit of it got inside the CPU through the front face of the CPU. As that happened the fan started running very fast and made noise. I tried to restart to see if it becomes fine, but the computer didn't start again. First it gave an error of "Alert! Air temperature sensor not detected" and didn't start. Next I tried again multiple times of starting the computer but then it gave some memory error. I was not able to start the computer. Incase there's a problem in hard disk or something related to memory, is there any way we can extract our work or data? I am scared if I am not able to extract my work in case some problem occurs like that. What options would I have? Help! EDIT: I have attached the photo here and you can see the area spilt in red circle. The hard drive electronics have been affected and internal speaker may also have been affected. Any advise on cleaning and if hard drive can work? EDIT 2: Are there any professional services offered to extract data from blemished hard disk, like this one, in case I am not able to run it personally?

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  • Offline cache copies in Windows file sharing

    - by netvope
    I frequently access media files (music or video) on a remote Windows file share. My Internet connection is not very fast, and I find it a waste of bandwidth when I repeatedly access the same files. For example, I may listen to the same song 30 times in a month. So, I would like to cache files I've used. I know Windows has an "Always available offline" feature but I dont' think it suit my needs. I don't want to make the whole share "available offline" as the remote Windows file share is huge (in terabytes). Making individual files "available offline" is tedious as the files are scattered in many different directories. It would be much more convenient if the system can simply cache those I've used. I could also manually make a local copy each time I use a file... but this is even more troublesome than making each file "available offline" Also The files on the share seldom change. Many of the files are rarely used. Some of the files are frequently used. I don't have a list of the most frequently used files. It would be the best if I could tell Windows to cache the last accessed 10GB, but apparently it doesn't have this feature. So I think the best way is to have a SMB/CIFS caching proxy. What do you think? I have a Linux box sitting around. Perhaps I should try to setup samba4?

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  • Windows 7 - svchost high cpu usage.

    - by Leonardo
    Hey guys! I'm having a problem with windows 7 x64 i though it was slow and all then i saw that the cpu usage was always around 80% and started digging through google. there's two svchost consuming around 30% each and in the resources monitor there's a system interrupts consuming 45% all the time, i trid closing the aplications and makes no diference. so i tried some other things that i've found on gloogle like disable system update but didn't work. i'd love some help here. i don't know if it will help but here's my specs: Core 2 duo 4400 ATI radeon 4850 4gb ram DDR2 thanks anyway for your attention :) EDIT So i run the program and i got this info, did i get it right? EDIT As you asked here it is, did i get it right now? the other tcp/ip there's nothing. thanks again! :D EDIT I tried somthing here, i run msconfig and took the services that one of the svchost was using out of the startup and now my cpu is around 50%, but i still would like to make this better, i can't lose that much cpu power just because windows... thanks. EDIT yeah there's nothing i can do here, going to install xp for a while, it's really weird...

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  • how to set cache control to public in iis 7.5

    - by ivymike
    I'm trying to set cache control header to max age using the following snippet in my web.config: <system.webServer> <staticContent> <clientCache cacheControlMode="UseMaxAge" cacheControlMaxAge="1.00:00:00" /> </staticContent> </system.webServer> Some how this isn't being reflected in the response. Instead I see a Cache-Control: private header on the responses. I'm using NancyFx framework (which is a layer on top of Asp.net). Is there any thing else I need to do ? Below are the reponse headers I receive: HTTP/1.1 200 OK\r\n Cache-Control: private\r\n Content-Type: application/x-javascript\r\n Content-Encoding: gzip\r\n Last-Modified: Mon, 19 Mar 2012 16:42:03 GMT\r\n ETag: 8ced406593e38e7\r\n Vary: Accept-Encoding\r\n Server: Microsoft-IIS/7.5\r\n Nancy-Version: 0.9.0.0\r\n Set-Cookie: NCSRF=AAEAAAD%2f%2f%2f%2f%2fAQAAAAAAAAAMAgAAADxOYW5jeSwgVmVyc2lvbj0wLjkuMC4wLCBDdWx0dXJlPW5ldXRyYWwsIFB1YmxpY0tleVRva2VuPW51bGwFAQAAABhOYW5jeS5TZWN1cml0eS5Dc3JmVG9rZW4DAAAAHDxSYW5kb21CeXRlcz5rX19CYWNraW5nRmllbGQcPENyZWF0ZWREYXRlPmtfX0JhY2tpbmdGaWVsZBU8SG1hYz5rX19CYWNraW5nRmllbGQHAAcCDQICAAAACQMAAADTubwoldTOiAkEAAAADwMAAAAKAAAAAkpT5d9aTSzL3BAPBAAAACAAAAACPUCyrmSXQhkp%2bfrDz7lZa7O7ja%2fIg7HV9AW6RbPPRLYLAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA%3d; path=/; HttpOnly\r\n X-AspNet-Version: 4.0.30319\r\n Date: Tue, 20 Mar 2012 09:44:20 GMT\r\n Content-Length: 1624\r\n

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  • High CPU usage in my digitalocean droplet

    - by Ibrahim Azhar Armar
    I am experiencing high CPU usage here is the stats i got from server, the consumption after every restart in 15 minutes go upto 100%, what could go wrong? I have a wordpress copy installed on the server which does not have much traffic, here is the stats that i got from using top command in server. top - 11:46:02 up 12 min, 3 users, load average: 40.89, 16.03, 6.11 Tasks: 132 total, 41 running, 91 sleeping, 0 stopped, 0 zombie Cpu(s): 24.3%us, 61.5%sy, 0.0%ni, 0.0%id, 4.0%wa, 0.0%hi, 0.0%si, 10.2%st Mem: 2050896k total, 1988656k used, 62240k free, 284k buffers Swap: 0k total, 0k used, 0k free, 4712k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 31 root 20 0 0 0 0 R 39 0.0 1:35.53 kswapd0 899 root 20 0 15988 172 0 S 14 0.0 0:05.00 irqbalance 418 syslog 20 0 243m 600 0 S 13 0.0 0:06.85 rsyslogd 944 mysql 20 0 1320m 53m 0 S 12 2.7 0:21.15 mysqld 2357 root 20 0 17344 532 164 R 11 0.0 0:14.27 top 960 root 20 0 246m 3816 0 S 3 0.2 0:08.18 php5-fpm 2431 www-data 20 0 344m 64m 908 R 2 3.2 0:04.23 apache2 2435 www-data 20 0 304m 63m 836 R 2 3.2 0:03.43 apache2 2413 www-data 20 0 349m 63m 920 R 2 3.2 0:07.51 apache2 2465 www-data 20 0 349m 64m 944 R 2 3.2 0:05.04 apache2 2518 www-data 20 0 307m 41m 1204 R 2 2.1 0:01.37 apache2 2406 www-data 20 0 346m 56m 1144 R 2 2.8 0:03.76 apache2 2456 www-data 20 0 345m 55m 1184 R 2 2.8 0:02.67 apache2 2373 www-data 20 0 351m 63m 784 R 2 3.2 0:11.09 apache2 2439 www-data 20 0 306m 35m 916 R 2 1.8 0:02.51 apache2 2450 www-data 20 0 345m 55m 1088 R 2 2.8 0:02.96 apache2 2486 www-data 20 0 299m 10m 876 R 2 0.5 0:01.19 apache2 2523 www-data 20 0 300m 27m 796 R 2 1.4 0:00.99 apache2

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  • Which CPU for XEN - LAMP testbed - Budget

    - by deploymonkey
    Dear serverfault knowledgeables, im in a decision dilemma right now, which I can't resolve due to lack of hands on experience. I need to build a testbed for basically virtualizing a LAMP application (os'ses not yet decided) including server side calculations. I'll opt for XEN since it seems better supported by cloud hosters at the moment. The hardware is for a proof of concept for a startup doing saas and might be used for closed live alpha/beta later on. After testing, the testbed might be a) deployed as a colocated white box server b) used as workstation Single socket is enough. We want to have ECC memory for reliability, this excludes most of the consumer line at intel. If intel CPU, then threaded cpu (HT) is preferred have at least 16 gig ram If justified by price and reliability is not too bad, a high quality desktop MB instead of a server MB would be worth a try It came down to the opteron 6128 vs. the xeon 5620 for me after a lot of research, but I don't necessarily have to be right. Which CPU is preferrable, concerning TCO (MB price, power requirements 24/7...) , Opteron 6128 or Xeon 5620? Which one offers better performance in real world applications? (Do You have any other suggestions I probably overlooked?) Thank You for Your consideration

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  • Can varnish cache files without specific extension or residing in specific directory

    - by pataroulis
    I have a varnish installation to cache (MANY) images that my service serves. It is about 200 images of around 4k per second and varnish happily serves them according to the following rule: if (req.request == "GET" && req.url ~ "\.(css|gif|jpg|jpeg|bmp|png|ico|img|tga|wmf)$") { remove req.http.cookie; return(lookup); } Now, the thing is that I recently added another service on the same server that creates thumbnails to serve but it does not add a specific extension. The files are of the following filename pattern: http://www.example.com/thumbnails/date-of-thumbnail/xxxxxxxxx.xx where xx are numbers, so xxxxxxxxx.xx could be 6482364283.73 (two numbers at the end) (actually this is the timestamp so I can keep extra info in the filename) That has the side effect that varnish does not cache them and I see them constantly being served by apache itself. Even though I can change the format from now on to create thumbs ending in .jpg, is there a way to change the vcl file of my varnish daemon to either cache everything under a directory (the thumbnails directory) or everything with two numbers at its extension? Let me know if I can provide any additional info ! Thanks!

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  • disk write cache buffer and separate power supply

    - by HugoRune
    Windows has a setting to turn off the write-cache buffer (see image) Turn off Windows write-cache buffer flushing on the device To prevent data loss, do not select this check box unless the device has a separate power supply that allows the device to flush its buffer in case of power failure. Is it feasible and economical to get such a "separate power supply" for the internal sata drives of a non-server PC? Under what name is such a power supply sold? I know that there are UPS devices that can be connected to external drives,but what is required to be able to switch this setting safely on for an internal disk? The setting has different descriptions in different version of windows Windows XP: Enable write caching on the disk This setting enables write caching in Windows to improve disk performance, but a power outage or equipment failure might result in data loss or corruption. Windows Server 2003: Enable write caching on the disk Recommended only for disks with a backup power supply. This setting further improves disk performance, but it also increases the risk of data loss if the disk loses power. Windows Vista: Enable advanced performance Recommended only for disks with a backup power supply. This setting further improves disk performance, but it also increases the risk of data loss if the disk loses power. Windows 7 and 8: Turn off Windows write-cache buffer flushing on the device To prevent data loss, do not select this check box unless the device has a separate power supply that allows the device to flush its buffer in case of power failure. This article by Raymond Chen has some more detailed information about what the setting does.

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  • Cisco 7206vxr cpu reducing

    - by naimson
    I have a 7206VXR (NPE-G2) . At the rate of 140 kpps i gain 80% of cpu . So i looking for ways how to reduce it? So i want to turn off netflow(but don't want to this,monitoring is highly important for me), but it will give me only 10-20% ? At this moment with 84kpps i have 58% sh processes cpu sorted give me this. PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process 109 163534600 537236763 304 35.38% 32.83% 16.85% 0 IP Input 67 829396 52280 15864 0.15% 0.01% 0.00% 0 Per-minute Jobs 68 5542736 3053476 1815 0.15% 0.18% 0.16% 0 Per-Second Jobs 51 635852 1116315 569 0.07% 0.03% 0.02% 0 Net Background 329 120396 4607274 26 0.07% 0.00% 0.00% 0 EIGRP-IPv4 Hello 105 50508 95032488 0 0.07% 0.05% 0.05% 0 IPAM Manager 6 4068580 476916 8531 0.00% 0.07% 0.05% 0 Check heaps 7 7768 3634 2137 0.00% 0.00% 0.00% 0 Pool Manager 8 0 1 0 0.00% 0.00% 0.00% 0 DiscardQ Backgro 10 8 708 11 0.00% 0.00% 0.00% 0 WATCH_AFS 5 0 1 0 0.00% 0.00% 0.00% 0 RO Notify Timers 12 0 2 0 0.00% 0.00% 0.00% 0 ATM VC Auto Crea 9 0 2 0 0.00% 0.00% 0.00% 0 Timers 11 0 2 0 0.00% 0.00% 0.00% 0 ATM AutoVC Perio 13 296 610532 0 0.00% 0.00% 0.00% 0 IPC Event Notifi 16 0 1 0 0.00% 0.00% 0.00% 0 IPC Zone Manager 17 3584 2980311 1 0.00% 0.00% 0.00% 0 IPC Periodic Tim 4 0 1 0 0.00% 0.00% 0.00% 0 EDDRI_MAIN 19 0 1 0 0.00% 0.00% 0.00% 0 IPC Process leve 20 0 1 0 0.00% 0.00% 0.00% 0 IPC Seat Manager 21 96 174453 0 0.00% 0.00% 0.00% 0 IPC Check Queue 14 4 50890 0 0.00% 0.00% 0.00% 0 IPC Dynamic Cach 3 0 1 0 0.00% 0.00% 0.00% 0 cpf_process_tpQ 24 756 305371 2 0.00% 0.00% 0.00% 0 IPC Keep Alive M 25 2340 610561 3 0.00% 0.00% 0.00% 0 IPC Loadometer 22 0 1 0 0.00% 0.00% 0.00% 0 IPC Seat RX Cont 15 0 1 0 0.00% 0.00% 0.00% 0 IPC Session Serv 18 1620 2980310 0 0.00% 0.00% 0.00% 0 IPC Deferred Por 29 0 1 0 0.00% 0.00% 0.00% 0 Exception contro sh run(greped): http://pastie.org/5483194 Hardware: c7200p-adventerprisek9-mz.151-4.M1.bin Cisco 7206VXR (NPE-G2) processor (revision A) with 917504K/65536K bytes of memory. Processor board ID 2xxxxxxx MPC7448 CPU at 1666Mhz, Implementation 0, Rev 2.2 6 slot VXR midplane, Version 2.1

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  • Fixing bent pins on a CPU

    - by Pekka
    While replacing a mainboard in a desktop machine (see related question), I did something stupid. I inserted the CPU into the new mainboard, but didn't check for the right position. When it didn't immediately lock in, I pressed slightly before realizing what was wrong. The result was a number of bent pins. I tried every tutorial that popped up when Googling "CPU bent pins" - using credit cards, sewing needles, and a hunting knife to get the pins back into position - but to no avail: For every pin I get straightened out, two others are bent. I have no problem getting individual pins straightened out, but my many attempts have led to many pins being slightly askew - enough for the CPU not to fit into the socket (An AMD X3 one). Maybe I just lack the motoric finesse. What I would need is some sort of a grid to fix all pins at once. It's a €50 processor so the loss is not catastrophic. But I thought before I go buy a new one, I thought I'd check here whether anybody knows some magic trick, or a cheap generally-available tool to fix this.

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  • Gain Quick Access to the Cache in Firefox

    - by Asian Angel
    Are you looking for a quick and simple way to view the contents of the cache in Firefox? Then you will definitely want to see how easy it can be using the CacheViewer extension. Note: CacheViewer is a front-end app for easily accessing and searching the memory cache. Before Viewing the cache in Firefox using “about:cache” provides some information about the contents but may not be the most efficient method available for some people. CacheViewer in Action Once you have installed the extension there are three easy ways to access your new cache viewer. The first is using the “CacheViewer Command” available in the “Tools Menu” and the second is using the keyboard shortcut “Ctrl + Shift + C”. The third way is by adding a “Toolbar Button” to your browser’s UI. All three work equally well…choose the method that best suits your personal needs. When you access the “CacheViewer Window” this is what it will look like. You may decide to resize it and move (or hide) some of the columns for the best viewing. You can easily scroll through the cache contents and preview images if desired as shown here. If you keep the “CacheViewer Window” open you can refresh it as you browse using the “Refresh Button” in the lower right corner. This is a nice, quick, and very simple way to access the cache on demand and save items to your hard-drive if desired. Note: The “CacheViewer” can also be set to open in a new tab instead (see “Options”). Options Choose whether “CacheViewer” opens in a separate window (default) or in a new tab. Conclusion If you want a quick and simple way to view the cache in Firefox then the CacheViewer extension is just what you have been looking for. Link Download the CacheViewer extension (Mozilla Add-ons) Similar Articles Productive Geek Tips Add a Cache Clearing Button to FirefoxSearch for Install Packages from the Ubuntu Command LineQuick Tip: Empty Internet Explorer 7 Cache when Browser is ClosedView Internet Explorer Cache Files the Easy WayQuick Hits: 11 Firefox Tab How-Tos TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Out of band Security Update for Internet Explorer 7 Cool Looking Screensavers for Windows SyncToy syncs Files and Folders across Computers on a Network (or partitions on the same drive) If it were only this easy Classic Cinema Online offers 100’s of OnDemand Movies OutSync will Sync Photos of your Friends on Facebook and Outlook

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  • Clarification On Write-Caching Policy, Its Underlying Options And How It Applies To Hard Drives And Solid-State Drives

    - by Boris_yo
    In last week after doing more research on subject matter, I have been wondering about what I have been neglecting all those years to understand write-caching policy, always leaving it on default setting. Write-caching policy improves writing performance and consists of write-back caching and write-cache buffer flushing. This is how I understand all the above, but correct me if I erred somewhere: Write-through cache / Write-through caching itself is not a part of write caching policy per se and it's when data is written to both cache and storage device so if Windows will need that data later again, it is retrieved from cache and not from storage device which means only improved read performance as there is no need for waiting for storage device to read required data again. Since data is still written to storage device, write performance isn't improved and represents no risk of data loss or corruption in case of power failure or system crash while only data in cache gets lost. This option seems to be enabled by default and is recommended for removable devices with no need to use function of "Safely Remove Hardware" on user's part. Write-back caching is similar to above but without writing data to storage device, periodically releasing data from cache and writing to storage device when it is idle. In my opinion this option improves both read and write performance but represents risk if power failure or system crash occurs with the outcome of not only losing data eventually to be written to storage device, but causing file inconsistencies or corrupted file system. Write-back caching cannot be enabled together with write-through caching and it is not recommended to be enabled if no backup power supply is availabe. Write-cache buffer flushing I reckon is similar to write-back caching but enables immediate release and writing of data from cache to storage device right before power outage occurs but I don't know if it applies also to occasional system crash. This option seem to be complementary to write-back cache reducing or potentially eliminating risk of data loss or corruption of file system. I have questions about relevance of last 2 options to today's modern SSDs in order to get best performance and with less wear on SSDs: I know that traditional hard drives come with onboard cache (I wonder what type of cache that is), but do SSDs also come with cache? Assuming they do, is this cache faster than their NAND flash and system RAM and worth taking the risk of utilizing it by enabling write-back cache? I read somewhere that generally storage device's cache is faster than RAM, but I want to be sure. Additionally I read that write-caching should be enabled since current data that is to be written later to NAND flash is kept for a while in cache and provided there is data that gets modified a lot before finally being written, holding of this data and its periodic release reduces its write times to SSD thereby reducing its wearing. Now regarding to write-cache buffer flushing, I heard that SSD controllers are so fast by themselves that enabling this option is not required, because they manage flushing. However, once again, I don't know if SSDs have their own onboard cache and whether or not it is faster than their NAND flash and system RAM because if it is, keeping this option enabled would make sense. Recently I have posted question about issue with my Intel 330 SSD 120GB which was main reason to do deeper research having suspicion of write-caching policy being the culprit of SSD's freezing issue assuming data being released is what causes freezes. Currently I have write-cache enabled and write-cache buffer flushing disabled because I believe SSD controller's management of write-cache flushing and Windows write-cache buffer flushing are conflicting with each other: Since I want to troubleshoot in small steps to finally determine the source of issue, I have decided to start with write-caching policy and the move to drivers, switching to AHCI later on and finally disabling DIPM (device initiated power management) through registry modification thanks to @TomWijsman

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  • What's So Smart About Oracle Exadata Smart Flash Cache?

    - by kimberly.billings
    Want to know what's so "smart" about Oracle Exadata Smart Flash Cache? This three minute video explains how Oracle Exadata Smart Flash Cache helps solve the random I/O bottleneck challenge and delivers extreme performance for consolidated database applications. Exadata Smart Flash Cache is a feature of the Sun Oracle Database Machine. With it, you get ten times faster I/O response time and use ten times fewer disks for business applications from Oracle and third-party providers. Read the whitepaper for more information. var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-13185312-1"); pageTracker._trackPageview(); } catch(err) {}

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  • My computer freezes after some minutes while watching dvb tv from kaffeine but only when i use the cpu scaling utilities

    - by digitalcrow
    My computer freezes after some minutes while watching dvb tv from kaffeine but only when i use the cpu scaling utilities to enter cpu on performance mode. It freezes completely repeating a small sound loop from tv. cant go to terminal etc. I have a phenom II 3,40 ghz dualcore cpu , but i unlocked the other two cores so now its quadcore. On Windows i don't have any problems and i use the performance mode all the time and never breaks. I'm really dissapointed....

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  • Can I copy large files faster without using the file cache?

    - by Veazer
    After adding the preload package, my applications seem to speed up but if I copy a large file, the file cache grows by more than double the size of the file. By transferring a single 3-4 GB virtualbox image or video file to an external drive, this huge cache seems to remove all the preloaded applications from memory, leading to increased load times and general performance drops. Is there a way to copy large, multi-gigabyte files without caching them (i.e. bypassing the file cache)? Or a way to whitelist or blacklist specific folders from being cached?

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