13 votes

How dangerous might it be - and what performance gains may be had - by turning vulnerability mitigations off on non-Internet facing servers?

The Linux kernel flag mitigations=[on|off] is a single toggle to easily enable/disable all available kernel mitigations for hardware vulnerabilities as listed here https://docs.kernel.org/admin-guide/...
  • 1,713
3 votes
Accepted

Will disk compression impact the performance of a MySQL database?

It will likely make little to zero difference in terms of performance. Unless your workload is heavily based on performing full table scans, MySQL performance is governed by IOPS/disk latency. If you ...
3 votes

Performance improvement for Innodb - High CPU

I hear multiple questions: How to ingest 50+ rows per second onto a slow HDD from IoT. How to migrate "old" data off the SSD onto HDD. How to deal with lots of tables (one per IoT). I'm ...
  • 2,218
3 votes

KVM: Best performance for all guests

Good read: Can you help me with my capacity planning? Before you deploy production services you will need to understand their usage profile and any interactions that could be detrimental to the ...
  • 4,991
2 votes

Will disk compression impact the performance of a MySQL database?

Based on my personal experience and this page compression of ZFS have insignificant effect on overall performance. Of course it depend on the hardware you have - slow CPU may lead to slow operations, ...
  • 4,292
2 votes

How dangerous might it be - and what performance gains may be had - by turning vulnerability mitigations off on non-Internet facing servers?

is the server really impossible to connect to even indirectly from outside your network? That's the first question you should ask yourself. If the LAN can be accessed from a machine that has 2 network ...
  • 141
2 votes

RAID Controller -- SAS Expander -- SATA drives. What max throughput can be expected?

With rare exceptions, expander cannot change the transfer speed between host and disk, so 6 Gbit/s per lane is the best you can get with SATA. SATA switching is also less efficient than for SAS, so ...
  • 9,232
2 votes

Dell PE RHEL 7 terrible performance

As you only mentioned ls -l / taking a long time (and not all directories, for example), one possibility is that your root inode got really large. You can check this with stat / and look at the ...
2 votes

Windows server standard, processes not able to utilize all physical CPU

As vidarlo has already mentioned, your CPUs have total 48 cores/96 logical processors (due to hyperthreading). According to Microsoft, SQL Server Web Edition supports up to 16 cores: Scale limits ...
1 vote

NPS4 on a Threadripper 3960x gives two nodes with no memory at all

Ryzen 5 3960x is a desktop part. There are not the same quality of balanced memory guides like there are for EPYC server CPUs. On EPYC, memory is really in quadrants of memory channel pairs. Not ...
1 vote

Discovering the speed of data transfer between my server and another server that I don't have access to

I presume you have nftables or iptables available. the commands below are for iptables. iptables -N ACCT_OUT #outbound accounting iptables -n ACCT_IN #inbound accounting iptables -A FORWARDING --dst &...
1 vote

Windows server standard, processes not able to utilize all physical CPU

Xeon Gold 5318Y has 24 cores. You have two sockets, for a total of 48 physical cores. It however supports hyper-threading, which means that some tasks can run concurrently on a single core. So the ...
  • 5,749
1 vote
Accepted

RAID Controller -- SAS Expander -- SATA drives. What max throughput can be expected?

The answer is 96Gbit/s total throughput and 48Gbit/s hypothetical write speed for RAID 10 in short. Described chain will perform on expected 12Gbit/s per lane between RAID Controller and SAS Expander. ...
  • 23
1 vote
Accepted

Disk speed on Azure Virtual Machine Scale Set is slower than advertised

Microsoft Support pointed out that the reason for the low throughput is that the block size on testing was too small. I verified this with a larger blocksize and I got the promised numbers. The reason ...
1 vote

Object Storage vs HDD Block Storage

Likely, the price difference is mainly due to the cost/performance of SSD vs HDD. Whether HDDs are fast enough depends on the rate that you're serving those images. The amount of data you store isn't ...
  • 9,232
1 vote
Accepted

40Gbit/s RAID10 - on a single raid adapter is it possible?

A PCIe 4.0 x 8 connector can theoretically handle 16 GT/s and 15.754 GB/s, which equates to a worst-case of approximately 126Gbps, far exceeding your 40Gbps network speed. Looking at a controller, if ...
  • 101k
1 vote

Performance improvement for Innodb - High CPU

Analysis of GLOBAL STATUS and VARIABLES: Observations: Version: 10.3.27-MariaDB-0+deb10u1 16 GB of RAM Uptime = 04:05:27; some GLOBAL STATUS values may not be meaningful yet. 1.58e+4 Queries/sec : ...
  • 2,218
1 vote
Accepted

Performance improvement for Innodb - High CPU

Rate Per Second = RPS Suggestions to consider for your OS and my.cnf [mysqld] section For your OS, ulimit -n 32768 # to increase Open Files limit for your load + other apps needs For this to persist ...
1 vote

VMWare Disk Performance

The DL380p g8 with the P420i and SSD perform badly sadly. For more details please see; Please see that answer; https://serverfault.com/a/732298/256639 By default, the SmartArray disables the disk's ...
  • 16.5k
1 vote
Accepted

What do results of Linux time wrapper tell me happened to this cp command?

P in this context means the ratio of CPU time this job got over total time elapsed. Near 100% means almost all of the time it was on CPU, and so was CPU constrained for those runs. In contrast to the ...
1 vote
Accepted

How to configure HAProxy to ignore client header `Pragma: no-cache`?

Web browsers send Cache-Control and Pragma headers that mess with HAProxy and make the caching virtually unusable due to its inability to cache if cache-control or pragma headers are "no-cache&...
  • 26
1 vote

DELL PowerEdge R740xd - NUMA - memory performance

This is obviously a late answer but I ran across this question. I specialize in doing a lot of this at work and unfortunately a complete answer on doing NUMA testing is long and nuanced. Here are some ...
1 vote

Nginx: Optimizing server response time for a HTTP cached website

There is a lot fundamentally wrong with your setup. First, you should not need NGIX at all. YOu already have a caching system in Cloudflare, use it. This one will be way closer than to the user than ...
  • 51.4k
1 vote

SMI generation / detection in GRUB / real mode vs. in Linux

Arguably, there is much more reason for System Management Interrupts (SMIs) happening during real mode than when a full fledged operating system is running. The BIOS Implementation Test Suite (BITS) ...

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