Author Archives: maru

This release of tier makes it possible to disable or enable data migration via sysfs. To disable migration: echo 1>/sys/block/tiera/tier/disable_migration To enable migration: echo 0>/sys/block/tiera/tier/disable_migration When migration is re-enabled the migration process will immediately wake up and start. This feature … Continue reading →

How TIER works Tier is a Linux kernel block device that aggregates multiple devices of different nature into one virtual block device. The idea is to combine ( expensive ) fast and ( affordable ) slow devices to build a … Continue reading →

Tier-0.2.0 adds crash recovery and some bug fixes. A brief benchmark of tier, flashcache and bcache with fio shows these results: flashcache read : io=16635MB, bw=56778KB/s, iops=14194 , runt=300017msec read : io=872528KB, bw=2908.4KB/s, iops=727 , runt=300007msec write: io=8237.5MB, bw=28117KB/s, iops=7029 … Continue reading →

This version of tier comes with some major changes. The caching layer has been removed from the code. EPRD can be used in cases where caching is needed. Also the block size has been changed so that TIER now uses … Continue reading →

Tier is a Linux kernel module that can be used to create a block device that allows automatically tiered storage. Tier can be used to aggregate up to 16 devices as one virtual device. Tier investigates access patterns to decide … Continue reading →

To get an idea of the efficiency of EPRD caching I repeated the lessfs benchmark test with EPRD caching the Intel 320 SSD. The Intel 320SSD was registered as /dev/sdc. EPRD was setup like this : ./eprd_setup -f /dev/sdc -m … Continue reading →

Introduction People frequently ask what the performance is that they may expect from Lessfs. This article will give an indication of what to expect. About the hardware All the tests are done using an Intel 5520HC system board with a … Continue reading →

Lessfs-1.5.11 now allows users to specify the cache size that hamsterdb will use internally. This version also solves a bug in configure.ac that would cause configure with –disable-debug to actually enable debugging. This bug caused users to report very low … Continue reading →

Lessfs-1.5.10 adds support for hamsterdb-2.0.1. A small change in the Hamsterdb API makes the transition from the 1.x series not completely transparent. Do not use Lessfs with hamsterdb-2.0 since it comes with a nasty bug. Please use the latest hamsterdb-2.0.1. … Continue reading →

Today I uploaded a kernel project that I call eprd. This kernel module allows you to create a persistent ram disk. It can also be used to use DRAM to cache disk IO. Of course this comes with all the … Continue reading →