Using LVM cache for storage tiering

SSDs are small, expensive but fast. HDDs are large and cheap, but slow. Lets combine the two technologies to get the speed of SSDs with the price and size of HDDs. This can be achieved with storage tiering using LVM cache. Hardware vs. Software solutions There are so called “Hybrid HDDs” on the market. The SSD part is relatively small and you can not tune that cache or getting any statistics about cache hits and cache misses. Further, modern SSD ….Read More

Using Data Deduplication and Compression with VDO on RHEL 7 and 8

Storage deduplication technology has been on the market for quite some time now. Unfortunately all of the implementations have been vendor specific proprietary software. With VDO, there is now an open source Linux native solution available. Red hat has introduced VDO (Virtual Data Optimizer) in RHEL 7.5, a storage deduplication technology bough with Permabit in 2017. Of course it has been open sourced since then. In contrast to ZFS which provides the same functionality on the file system level, VDO ….Read More

Leveraging Network-Bound Disk Encryption at Enterprise Scale

Network-Bound Disk Encryption (NBDE) adds scaling to LUKS by automated disk unlocking on system startup. Why should I encrypt disks? If you dont want to see your corporate and private data leaked, you should do so as an additional security measure. Use cases There are basically two use cases for disk encryption. The first one is to prevent data leaks when a device gets stolen or lost (mobile computers, unsecured server rooms etc.). Theft of devices is usually not a ….Read More

Building a virtual CEPH storage cluster

This post will guide you trough the procedure to build up a testbed on RHEL7 for a complete CEPH cluster. At the end you will have an admin server, one monitoring node and three storage nodes. CEPH is a object and block storage mostly used for virtual machine images and bulk BLOBS such as video- and other media. It is not intended to be used as a file storage (yet). Machine set up I’ve set up five virtual machines, one ….Read More

Creating and managing iSCSI targets

If you want to create and manage iSCSI targets with Fedora or RHEL, you stumble upon tgtd and tgtadm. This tools are easy to use but have some obstacles to take care of. This is a quick guide on how to use tgtd and tgtadm. iSCSI terminology In the iSCSI world, we not taking about server and client, but iSCSI-Targets, which is the server and iSCSI-Initiators which are the clients Install the tool set It is just one package to ….Read More

Confused about write barriers on file systems…

As ext3 is already known as a very robust file system why is the default mount option still barrier=0? The problem is LVM and the device mapper. They¬† do not support barriers. When mounting ext3 on a LV, the option barrier=1 it¬†should be ignored and a warning written. So far so good. Trying this brings a lot of confusion. According to a Red Hat bugzilla entry one should get a warning, but no signs of that neither in /var/log/messages nor ….Read More

How are jornaling options affect performance of the ext3 filesystem

The need for speed Everyone looks for the optimum of speed in its servers. Todays servers have plenty of spare CPU power and RAM is dirty cheap. Todays common bottleneck is storage. One way to solve the bottleneck is trowing money on it, the other smarter way is choosing the best matching file system and it options for the purpose of the server. On Linux systems a bunch of file systems is available and ready to use. There are some ….Read More