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  • Apache is spawning more and more processes!!

    - by erotsppa
    We have a LAMP setup that is working prety good for half a year. All of a sudden today the apache server (mysql servers are not on this box) started to die. It seems to have started to spawn more and more processes over time. Eventually it will consume all the memory and the server would just die. We are using prefork. In the mean time what we are doing is just added more ram and increased the MaxClients and ServerLimit parameter to 512. We're just prolonging the crash. The number still goes up slowly. Maybe in a day, it would reach that limit. What is going on? We only have around 15-20 request per second. We have 1Gb memory and it's not half used, there's no swapping going on. Why is apache creating more and more processes? It's almost like theres a leak somewhere! The database boxes are fine, they are not causing a delay to requests. We tested some queries everything is quick!

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  • How to mirror filesystems with millions of hardlinks?

    - by Thomas Berger
    We have one big problem at the moment: We need to mirror a filesystem for one of our customers. Thats usual not really a problem, but here it is: On this filesystem there is one folder with millions of hardlinks (yes! MILLIONS!). rsync requires more then 4 days to just build the filelist. We use the following rsync options: rsync -Havz --progress serverA:/data/cms /data/ Has anyone a idea how to speed up this rsync, or use alternatives? We could not use dd as the target disk is smaller then the source.

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  • Apache2 BufferedLogs On - anybody using it ?

    - by Qiqi
    Greetings, I am wondering, whether anybody is using BufferedLogs On with Apache2 and found any issues ? Feature is marked as experimental, but for many years now, so I guess it's rather pretty stable. I am running some servers with constrained disk IO capacity at the moment, so I turned it on hoping that even a small benefit could help in the long run ;-) I do have several to several hundreds requests per seconds so by my thoughts there is really no need to write to log after each request, cause honestly I don't think that my filesystem is the best handler for many unnecessary writes. (OCFS2 shared among several DomUs in the Xen)

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  • Extracting one file from archive: 7-zip requires decompressing entire archive?

    - by siikamiika
    I've noticed that when browsing an archive containing multiple files with 7-zip 9.20 Windows GUI, extracting one file for previewing takes significantly longer with .7z than .rar archives. With .7zips it also cycles through the filenames in the archive. To me it looks like decompressing the entire archive and keeping just one file. Is there a setting in 7-zip (current or beta/alpha versions) that allows RAR-like behavior?

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  • Pros/cons to turning off cable modem

    - by Jay
    A little off the wall perhaps, but ... I have a cable modem and a router for a wireless home network. Is it a good or a bad idea to turn it off at night and during the day when we're all at work or school? Or should I leave it on 24/7. I was thinking that leaving it on constantly makes me more vulnerable to hackers, not to mention wasting electricity. (Though I'd guess the amount of electricity used by a cable modem and a router is probably pretty trivial. Still, every little bit helps.) When I have turned it off and turned it on again, it takes several minutes for it to go through its little dialog with the cable company and get me connected to the Internet again, which is annoying but not a big deal. Anyone know any good reasons one way or the other?

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  • Why might apache2 use 100% of CPU at startup?

    - by QuantumMechanic
    This is apache 2.2.14 on SLES9. Out of nowhere (i.e. it had been working fine for ages) I am seeing apache2 suddenly start using 100% of the CPU at startup, and never completing startup. Nothing is getting written to /var/log/error_log (when it did back when things were OK). ps only shows the main httpd process and not any of the spawned threads. When things were OK, it would show the spawned threads. So it appears httpd is going into some sort of infinite loop right at startup and isn't even completing startup. It's not an issue of being overloaded by connections -- this happens even when nothing is trying to contact it. The config files haven't changed (or at least they haven't changed in a way that changed their last-modified time). I've tried added -e debug -E /var/log/apache2/startup_info to the command line, but nothing is put in the file. Any ideas what could be happening?

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  • PHP5 without PHP4 compatibility

    - by Serty Oan
    This is the opposite question of this one. My purpose is that there is no need when you write only PHP5 code to have PHP4 compatibility. It is not helpful at all and due to differences between object models in those two version, it must be penalizing on interpreter performances (or am I wrong ?). So my questions are : is it possible to recompile PHP5 without retrocompatibility with PHP4 or to disable it in any other way to gain performances ? if it is not possible, is there a project somewhere which aim that goal ?

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  • Is it reasonable that a random disk seek & read costs ~16ms?

    - by fzhang
    I am frustrated about the latency of random reading from a non-ssd disk. Based on results from following test program, it speeds ~16 ms for a random read of just 512 bytes without help of os cache. I tried changing 512 to larger values, such as 25k, and the latency did not increase as much. I guess it is because the disk seek dominates the time. I understand that random reading is inherently slow, but just want to be sure that ~16ms is reasonable, even for non-ssd disk. #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> #include <sys/unistd.h> #include <fcntl.h> #include <limits.h> #include <stdio.h> #include <string.h> int main(int argc, char** argv) { int fd = open(argv[1], O_RDONLY); if (fd < 0) { fprintf(stderr, "Failed open %s\n", argv[1]); return -1; } const size_t count = 512; const off_t offset = 25990611 / 2; char buffer[count] = { '\0' }; struct timeval start_time; gettimeofday(&start_time, NULL); off_t ret = lseek(fd, offset, SEEK_SET); if (ret != offset) { perror("lseek error"); close(fd); return -1; } ret = read(fd, buffer, count); if (ret != count) { fprintf(stderr, "Failed reading all: %ld\n", ret); close(fd); return -1; } struct timeval end_time; gettimeofday(&end_time, NULL); printf("tv_sec: %ld, tv_usec: %ld\n", end_time.tv_sec - start_time.tv_sec, end_time.tv_usec - start_time.tv_usec); close(fd); return 0; }

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  • Samba PDC share slow with LDAP backend

    - by hmart
    The scenario I have a SUSE SLES 11.1 SP1 machine as Samba master PDC with LDAP backend. In one share there are Database files for a Client-Server application. I log XP and Windows 7 machines to the local domain (example.local), the login is a little slow but works. In the client computers have an executable which opens, reads and writes the database files from the server share. The Problem When running Samba with LDAP password backend the client application runs VERY SLOW with a maximum transfer rate of 2500 MBit per second. If disable LDAP the client app speed increases 20x, with transfer rate of 50Mbit/sec and running smoothly. I'm doing test with just two users and two machines, so concurrency, or LDAP size shouldn't be the problem here. The suspect LDAP, Smb.conf [global] section configuration. The Question What can I do? I've googled a lot, but still have no answer. Slow smb.conf WITH LDAP [global] workgroup = zmartsoft.local passdb backend = ldapsam:ldap://127.0.0.1 printing = cups printcap name = cups printcap cache time = 750 cups options = raw map to guest = Bad User logon path = \\%L\profiles\.msprofile logon home = \\%L\%U\.9xprofile logon drive = P: usershare allow guests = Yes add machine script = /usr/sbin/useradd -c Machine -d /var/lib/nobody -s /bin/false %m$ domain logons = Yes domain master = Yes local master = Yes netbios name = server os level = 65 preferred master = Yes security = user wins support = Yes idmap backend = ldap:ldap://127.0.0.1 ldap admin dn = cn=Administrator,dc=zmartsoft,dc=local ldap group suffix = ou=Groups ldap idmap suffix = ou=Idmap ldap machine suffix = ou=Machines ldap passwd sync = Yes ldap ssl = Off ldap suffix = dc=zmartsoft,dc=local ldap user suffix = ou=Users

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  • nginx+php-fpm help optimize configs

    - by Dmitro
    I have 3 servers. First server (CPU - model name: 06/17, 2.66GHz, 4 cores, 8GB RAM) have nginx as load balancer with next config upstream lb_mydomain { server mydomain.ru:81 weight=2; server 66.0.0.18 weight=6; } server { listen 80; server_name ~(?!mydomain.ru)(.*); client_max_body_size 20m; location / { proxy_pass http://lb_mydomain; proxy_redirect off; proxy_set_header Connection close; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_pass_header Set-Cookie; proxy_pass_header P3P; proxy_pass_header Content-Type; proxy_pass_header Content-Disposition; proxy_pass_header Content-Length; } } And configs from nginx.conf: user www-data; worker_processes 5; # worker_priority -1; error_log /var/log/nginx/error.log; pid /var/run/nginx.pid; events { worker_connections 5024; # multi_accept on; } http { include /etc/nginx/mime.types; access_log /var/log/nginx/access.log; sendfile on; default_type application/octet-stream; #tcp_nopush on; keepalive_timeout 65; tcp_nodelay on; gzip on; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; # PHP-FPM (backend) upstream php-fpm { server 127.0.0.1:9000; } include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } And config php-fpm: listen = 127.0.0.1:9000 ;listen.backlog = -1 ;listen.allowed_clients = 127.0.0.1 ;listen.owner = www-data ;listen.group = www-data ;listen.mode = 0666 user = www-data group = www-data pm = dynamic pm.max_children = 80 ;pm.start_servers = 20 pm.min_spare_servers = 5 pm.max_spare_servers = 35 ;pm.max_requests = 500 pm.status_path = /status ping.path = /ping ;ping.response = pong request_terminate_timeout = 30s request_slowlog_timeout = 10s slowlog = /var/log/php-fpm.log.slow ;rlimit_files = 1024 ;rlimit_core = 0 ;chroot = chdir = /var/www ;catch_workers_output = yes ;env[HOSTNAME] = $HOSTNAME ;env[PATH] = /usr/local/bin:/usr/bin:/bin ;env[TMP] = /tmp ;env[TMPDIR] = /tmp ;env[TEMP] = /tmp ;php_admin_value[sendmail_path] = /usr/sbin/sendmail -t -i -f [email protected] ;php_flag[display_errors] = off ;php_admin_value[error_log] = /var/log/fpm-php.www.log ;php_admin_flag[log_errors] = on ;php_admin_value[memory_limit] = 32M In top I see 20 php-fpm processes which use from 1% - 15% CPU. So it's have high load averadge: top - 15:36:22 up 34 days, 20:54, 1 user, load average: 5.98, 7.75, 8.78 Tasks: 218 total, 1 running, 217 sleeping, 0 stopped, 0 zombie Cpu(s): 34.1%us, 3.2%sy, 0.0%ni, 37.0%id, 24.8%wa, 0.0%hi, 0.9%si, 0.0%st Mem: 8183228k total, 7538584k used, 644644k free, 351136k buffers Swap: 9936892k total, 14636k used, 9922256k free, 990540k cached Second server(CPU - model name: Intel(R) Xeon(R) CPU E5504 @ 2.00GHz, 8 cores, 8GB RAM). Nginx configs from nginx.conf: user www-data; worker_processes 5; # worker_priority -1; error_log /var/log/nginx/error.log; pid /var/run/nginx.pid; events { worker_connections 5024; # multi_accept on; } http { include /etc/nginx/mime.types; access_log /var/log/nginx/access.log; sendfile on; default_type application/octet-stream; #tcp_nopush on; keepalive_timeout 65; tcp_nodelay on; gzip on; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; # PHP-FPM (backend) upstream php-fpm { server 127.0.0.1:9000; } include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } And config of php-fpm: listen = 127.0.0.1:9000 ;listen.backlog = -1 ;listen.allowed_clients = 127.0.0.1 ;listen.owner = www-data ;listen.group = www-data ;listen.mode = 0666 user = www-data group = www-data pm = dynamic pm.max_children = 50 ;pm.start_servers = 20 pm.min_spare_servers = 5 pm.max_spare_servers = 35 ;pm.max_requests = 500 ;pm.status_path = /status ;ping.path = /ping ;ping.response = pong ;request_terminate_timeout = 0 ;request_slowlog_timeout = 0 ;slowlog = /var/log/php-fpm.log.slow ;rlimit_files = 1024 ;rlimit_core = 0 ;chroot = chdir = /var/www ;catch_workers_output = yes ;env[HOSTNAME] = $HOSTNAME ;env[PATH] = /usr/local/bin:/usr/bin:/bin ;env[TMP] = /tmp ;env[TMPDIR] = /tmp ;env[TEMP] = /tmp ;php_admin_value[sendmail_path] = /usr/sbin/sendmail -t -i -f [email protected] ;php_flag[display_errors] = off ;php_admin_value[error_log] = /var/log/fpm-php.www.log ;php_admin_flag[log_errors] = on ;php_admin_value[memory_limit] = 32M In top I see 50 php-fpm processes which use from 10% - 25% CPU. So it's have high load averadge: top - 15:53:05 up 33 days, 1:15, 1 user, load average: 41.35, 40.28, 39.61 Tasks: 239 total, 40 running, 199 sleeping, 0 stopped, 0 zombie Cpu(s): 96.5%us, 3.1%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.4%si, 0.0%st Mem: 8185560k total, 7804224k used, 381336k free, 161648k buffers Swap: 19802108k total, 16k used, 19802092k free, 5068112k cached Third server is server with database postgresql. Also i try ab -n 50 -c 5 http://www.mydomain.ru/ And I get next info: Complete requests: 50 Failed requests: 48 (Connect: 0, Receive: 0, Length: 48, Exceptions: 0) Write errors: 0 Total transferred: 9271367 bytes HTML transferred: 9247767 bytes Requests per second: 1.02 [#/sec] (mean) Time per request: 4882.427 [ms] (mean) Time per request: 976.486 [ms] (mean, across all concurrent requests) Transfer rate: 185.44 [Kbytes/sec] received Please advise how can I make lower level of load average?

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  • Drawbacks of installing linux on usb stick?

    - by Znarkus
    I am setting up a router/nas/http/whatever server based on an ION mini-ITX board. I've installed Ubuntu Server on an old 160 GB drive, but it generates a lot more heat and vibrates more than my other new drive (storage). It just doesn't fit the concept, and worse: it takes up a SATA port. As SSD's are crazy expensive I'm thinking of buying an extra 4 GB USB stick, and raid0 it. From my point of view, these are the pros/cons: Pros Low power consumption No vibrations No heat Smaller Get to buy new, larger USB stick (:D) Cons Shorter life time Slower Raid 0 More work maintaing/installing? I think the pros overweighs the cons. Shorter life time and raid 0 is countered by regular backups of the configs/settings. Slower is partially countered by raid 0, and I don't know about the last one. What do You think? Experience? Another solution?

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  • Mac has become insanely slow : Processes SystemUIServer, UserEventAgent and loginwindow using a lot of memory

    - by SatheeshJM
    I have been using my Mac for for many months without any problem. But recently all of a sudden the Mac became insanely slow. I opened Activity Manager to see what was happening. For three processes SystemUIServer, UserEventAgent and loginwindow, the memory gradually increases and reaches upto 2 GB for each process. This completely hangs up my Mac. I tried the following : 1. Restart Mac 2. Restart Mac in safe mode 3. Manually kill the processes 4. Remove Date and Time from Menu bar(this was supposed to be the problem for the SysteUIServer process's memory according to many users) 5. Removed the externally connected keyboard and mouse(some had suggested this for UserEventAgent's memory) No luck with any of those. The moment I log in, the memory spikes up. Any idea what the hell is happening? Please help.

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  • SQL Server 2008 Web VS SQL Server 2008 Enterprise

    - by Jeremy
    I wrote an application a few months ago, and was hosting it out of our offices on a workstation with an Intel Core 2 Quad Q8200 @ 2.33GHz, 8 GB RAM, Windows Server 2008 Enterprise and SQL Server 2008 Enterprise. Both the webserver and database server were run on the same machine. We had a huge influx in traffic, and moved ClubUptime.com, and got 2 of their top teir windows VMs. The Database server runs Windows 2008 R2 Standard and SQL Server 2008 R2 Web on 8 GB ram and an Intel Xeon e5620 @ 2.40GHz. Ever since switching, the database which used to run at around 400MB in RAM now runs at around 4-7GB, and there haven't been any changes to it (other than a couple columns here and there). Our traffic has quadrupled, and our DB is 6 GB on disk, why would SQL server take up 7 GB if the DB is only 6. And why would it be storing the ENTIRE database in memory? Another thing is why growing 4 times in size did the database's memory footprint grow 12 times? Last question: Why does the CPU peg at 100% now where it didn't before? The design is simple, VERY few joins, NO subqueries. I am just at a loss, unless it is the SQL server edition, or the fact that I moved from real hardware to a VM.

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  • Very low throughput on 10GbE network

    - by aix
    I have two Linux machines, each equipped with a Solarflare SFN5122F 10GbE NIC. The two NICs are connected together with an SFP+ Direct Attach cable. I am using netperf to measure TCP throughput between the two machines. On one box, I run: netserver and on the other: netperf -t TCP_STREAM -H 192.168.x.x -- -m 32768 I get: MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.x.x (192.168.x.x) port 0 AF_INET Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 32768 10.02 1321.34 The measured throughput is 1.3Gb/s. This is 7.5x below the theoretical maximum, and only 30% faster than 1GbE. What steps can I take to troubleshoot this?

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  • Does this prove a network bandwidth bottleneck?

    - by Yuji Tomita
    I've incorrectly assumed that my internal AB testing means my server can handle 1k concurrency @3k hits per second. My theory at at the moment is that the network is the bottleneck. The server can't send enough data fast enough. External testing from blitz.io at 1k concurrency shows my hits/s capping off at 180, with pages taking longer and longer to respond as the server is only able to return 180 per second. I've served a blank file from nginx and benched it: it scales 1:1 with concurrency. Now to rule out IO / memcached bottlenecks (nginx normally pulls from memcached), I serve up a static version of the cached page from the filesystem. The results are very similar to my original test; I'm capped at around 180 RPS. Splitting the HTML page in half gives me double the RPS, so it's definitely limited by the size of the page. If I internally ApacheBench from the local server, I get consistent results of around 4k RPS on both the Full Page and the Half Page, at high transfer rates. Transfer rate: 62586.14 [Kbytes/sec] received If I AB from an external server, I get around 180RPS - same as the blitz.io results. How do I know it's not intentional throttling? If I benchmark from multiple external servers, all results become poor which leads me to believe the problem is in MY servers outbound traffic, not a download speed issue with my benchmarking servers / blitz.io. So I'm back to my conclusion that my server can't send data fast enough. Am I right? Are there other ways to interpret this data? Is the solution/optimization to set up multiple servers + load balancing that can each serve 180 hits per second? I'm quite new to server optimization, so I'd appreciate any confirmation interpreting this data. Outbound traffic Here's more information about the outbound bandwidth: The network graph shows a maximum output of 16 Mb/s: 16 megabits per second. Doesn't sound like much at all. Due to a suggestion about throttling, I looked into this and found that linode has a 50mbps cap (which I'm not even close to hitting, apparently). I had it raised to 100mbps. Since linode caps my traffic, and I'm not even hitting it, does this mean that my server should indeed be capable of outputting up to 100mbps but is limited by some other internal bottleneck? I just don't understand how networks at this large of a scale work; can they literally send data as fast as they can read from the HDD? Is the network pipe that big? In conclusion 1: Based on the above, I'm thinking I can definitely raise my 180RPS by adding an nginx load balancer on top of a multi nginx server setup at exactly 180RPS per server behind the LB. 2: If linode has a 50/100mbit limit that I'm not hitting at all, there must be something I can do to hit that limit with my single server setup. If I can read / transmit data fast enough locally, and linode even bothers to have a 50mbit/100mbit cap, there must be an internal bottleneck that's not allowing me to hit those caps that I'm not sure how to detect. Correct? I realize the question is huge and vague now, but I'm not sure how to condense it. Any input is appreciated on any conclusion I've made.

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  • use of tcp_delack_min on redhat linux (kernel 2.6.18)

    - by user41466
    Hello, we're moving from Solaris to Redhat Linux, and trying to duplicate our low-latency setup, that, on solaris, includes the ndd settings related to TCP NO DELAY, and NAGLE ALGORITHM. I got the impression that those parameters are not all configurable system-wide, but still found some info. we have configured our applications to run with no nagle algorithm, but that is not sufficient. we have found an interesting RH article talking presenting the tcp_delack_min parameter, however, when browsing /proc/sys/net/ipv4/ , I can't find it there. would it be safe to assume that simply "adding" the parameter as it's said on the doc would be enough, or rather that the option is not supported by this version (would be strange, as RH specify that it "can be performed on a standard Red Hat Enterprise Linux installation") ? any other idea / recommendation to improve latency further ? thanks

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  • What TrustLeap G-WAN for?

    - by Rowan
    Hi, Some people said that TrustLeap G-WAN ( http://trustleap.ch/ ) is very fast. But after reading the manual, I dont see guide to use G-WAN with PHP or Python. So, what this application server for? Is it only works only for C language? Thanks in advance

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  • Monitoring the Server load In Windows NT and triggering a scheduled task

    - by Gnanesh
    Hi, I am having the following problem. I am running a Windows NT server. I need to monitor the server utilization continuously (automated process) and need to know if the server load is high. And if it high I need to trigger a scheduled task. Can we write a VB script in order to do this? Can someone please help me? Kindly let me know in case you require more info on this Thanks

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  • Best way to monitorize a Grid of computers?

    - by marc.riera
    Hello, I've installed sun grid in 10 nodes, and one virtual master host. Now I have to monitorize all the resourses prior to launch it to production, but I don't know which is the best way. I've tried using xml-qstat, but it seems unstable. Any tips or suggestions? Anyone got experience on this? thanks.

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  • High disk I/O - jbd2/sda2-8 process

    - by Evan Hamlet
    I have run a file server on a CentOS 5.8 final server. My only concern at the moment is what appears to be intermittent but continuous high disk I/O activity causing a general slowdown because of jbd2/sda2-8 process. jbd2/sda2-8 is making use of /dev/sda2, which is the 2nd partition of the first harddrive (IE: root partition). More info: using "iotop" the culprit appears to be "jbd2/sda1-8" making writes every second, which appears to be a kernel process associated with journaling on the ext4 filesystem, if my googling around is correct. I see "jbd2/sda2-8" appearing here every now and then, but certainly not every 3 seconds.. when idle, it appears about 1 or 2 times per minute. When I'm using the system, it appears more frequently. ATOP results: http://grabilla.com/02b14-8022db2e-4eb9-4f10-8e10-d65c49ad7530.png IOTOP results: http://grabilla.com/02b14-cf74b25d-4063-4447-9210-7d1b9b70e25b.png HTOP results: grabilla. com/02b14-ad8cad0e-89b0-46d3-849d-4fd515c1e690.png jbd2/sda2-8 is the processes I see with iotop making writes on disk even though it's not in use at all. Does someone has any idea how could I solve the high disk usage caused jbd2/sda2-8 process?

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  • Slow transfer with memory stick (819 kb/s)

    - by Nrew
    What do I do to optimize the file transfer rate of a Memory Stick Duo? The file transfer was not like this when it was still new. Can reformatting give new life to a memory stick? It takes about 20 minutes just to transfer 1Gb of file from computer to memory stick. The computer is decent enough. 2.50Ghz processor, 2Gb ram.

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  • SQL Server Management Studio Reports: Why no open transactions?

    - by Sleepless
    On a server with several hundred user connections, when I open the SQL Server 2008 SP1 Management Studio report "Database - User Statistics", the result page shows the following results: Login Name: appUser Active Sessions: 243 Active Connections: 243 Open Transactions: 374 Still, when I open the report "Database - All Transactions" on the same DB, it doesn't show any connections ("Currently, there are no transactions running for [Database Name] Database"). What gives? Is this a bug in Management Studio? This is not the only report where this kind of behavious happens... Thanks all!

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  • Throughput = BS * IOPS?

    - by Marvin
    I've seen in many places that throughput = bs * iops should be true. For example writing at 128k block size to a SAS disk that can support 190 IOPS should give a throughput of ~23 MBps - 23.75(MBs) = 128(BS)*190(SAS-15 IOPS)/1024. Now when I tested it in a VM against a monster NetApp filer I got theses results: # dd if=/dev/zero of=/tmp/dd.out bs=4k count=2097152 8589934592 bytes (8.6 GB) copied, 61.5996 seconds, 139 MB/s To view the IO rate of the VM I used iostat and esxtop, and they both showed around 250 IOPS. So to my understanding the throughput was supposed to be ~1000k: 1000(KBs) = 4(BS)*250(IOPS). dd of 8GB is twice the size of RAM of course, so no page caching here. What am I missing? Thanks!

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