Questions tagged [disk-cache]

Disk-cache: reserved area in RAM to speed-up disk access

A disk cache is a cache memory that is used to speed up the process of storing and accessing data from the host hard disk. It enables faster processing of reading/writing, commands and other input and output process between the hard disk, the memory and computing components.

The memory can be part of the disk drive itself (sometimes called a hard disk cache or buffer) or it can be general-purpose RAM in the computer that is reserved for use by the disk drive (sometimes called a soft disk cache). Hard disk cachesare more effective, but they are also much more expensive, and therefore smaller. Nearly all modern disk drives include a small amount of internal cache.

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How much does HDD cache matter with Linux softraid?

I'm in a process of renewing/expanding my disk sets, but not quite sure what kind of disks to get, cache-wise. What difference does disk cache amount of 16/32/64MB do, in capacities of, say, 1/1.5/2TB SATA disks? The disks will be used in a webapp…
Jawa
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How to ensure HDD Write Caching is disabled on MS Storage Spaces

I have a Storage Spaces pool on a server that is not currently power protected. It consists only of mechanical hard drives. I want to compare performance of write caching enabled vs disabled so I can make a decision about how much of a priority…
Cyanara
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On a system with 64GB mem the Linux Buffer run full while copying with dd to dev null and io stops till manual drop_caches

I am running a server with linux software raid 10. It is a dual CPU system with 64GB Ram. 2x16GB dimms related to each of the CPUs. I want to use dd to backup kvm virtual machines and run into a serious io problem. First I thought is related to the…
user219392
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varnish delete least requested files

I see that varnish can be configured to set -smalloc or -sfile with a certain size. I want to set a file cache of 1G such that least requested files are deleted first when cache is full. Is this possible in varnish? Is there another reverse proxy…
nurettin
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Would a PHP application benefit from being served from a RAM drive?

I am in charge of hosting a PHP application that is large and slow, but easy to scale. The application is entirely static, with writable disk storage needed. We've profiled the application, and the main bottleneck appears to come from loading the…
Tom Marthenal
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Why would diskspd perform better without cache?

We are currently investigating high disk latency on a Windows server 2012 r2 that run as an SQL server. It is a virtual machine under VMware and the datastore of the faulty disk is linked with a very high performance LUN on a SAN. The SAN shows very…
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Active process swapping despite free memory

For some reason our system starts swapping (actively used memory) at around 60GB used memory. (see edit below, it seems I/O and disk cache usage, even of previously run processes has an effect) Turning it off (swapoff-a) for test lead to bad_alloc's…
b.buchhold
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How to increase the disk write buffer for rsync on Mac OS X?

I have to copy some TB of data from one external drive to another (mostly ~400 MB files). The source is NTFS-formatted USB2 and the best read speed I can get from it is 7MB/s. The target is HFS+ USB3 and the write speed is considerably higher than…
entonio
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Apache when to use mod_cache? disk_cache vs memory_cache?

I'm making use of Apache 2.4.10 on Ubuntu 15.04 and my entire server runs on a SSD and is virtualised in Hyper-V. When should I enable mod cache in Apache 2.4? Currently I have pretty good TTFB for static files. (0.015 - 0.020 seconds TTFB, when…
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Would the data on the RAID Card Cache and Drive Cache be lost when a kernel panic happens?

Is a BBU necessary when you have A+B power? Would the data on the RAID Card Cache and Drive Cache be lost when a kernel panic happens and you are forced to do a cold reset?
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Linux filesystem page cache - hot or not

How can you tell how much of the filesystem cache is hot (frequently accessed) or not? The use case would be determining when you are approaching the limits of your memory but before you actually hit them (and see a spike in page faults) Essentially…
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Why is mongod not using all available RAM?

We have an mongod instance runnning on a VM, and it doesn't seem to be using all available memory. It's page-faulting significantly more than usual, and the system's performance has been significantly degraded lately. More specifically, if I htop…
Thanatos
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ram disk mirroring part of physical disk

What I would like to do/have is: Some kind of application/driver that creates a RAM drive/partition that is actually assigned a drive letter (eg. D:). This drive letter should be based on/mirroring a specific directory of a physical directory (eg.…
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CentOS VM only using a third of available memory

I have a VM slice running CentOS, on Parallels. Here is the output of free -m [root@server ~]# free -m total used free shared buffers cached Mem: 960 272 687 0 0 …
soupagain
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High disk I/O activity in CentOS server

I have about 16 websites in a CentOS dedicated, and I am having some problems on high traffic hours, it seems to be a high disk I/O activity causing a general slowdown. I've installed atop and this is what I see on the bottom (the server has been…
triiim
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