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Cheap NAS Devices Suck

There are some really good Network Attached Storage (NAS) devices on the market. NetApp is one company that is known for making good products [1]. The advantage of a NAS is that you have a device with NVRAM for write-back caching, a filesystem that supports all the necessary features for best performance (NetApp developed their […]

Starting with BTRFS

Based on my investigation of RAID reliability [1] I have determined that BTRFS [2] is the Linux storage technology that has the best potential to increase data integrity without costing a lot of money. Basically a BTRFS internal RAID-1 should offer equal or greater data protection than RAID-6.

As BTRFS is so important and so […]

More DRBD Performance tests

I’ve previously written Some Notes on DRBD [1] and a post about DRBD Benchmarking [2].

Previously I had determined that replication protocol C gives the best performance for DRBD, that the batch-time parameters for Ext4 aren’t worth touching for a single IDE disk, that barrier=0 gives a massive performance boost, and that DRBD gives a […]

5 Principles of Backup Software

Everyone agrees that backups are generally a good thing. But it seems that there is a lot less agreement about how backups should work. Here is a list of 5 principles of backup software that seem to get ignored most of the time:

(1/5) Backups should not be Application Specific

It’s quite reasonable for people […]

Reliability of RAID

ZDNet has an insightful article by Robin Harris predicting the demise of RAID-6 due to the probability of read errors [1]. Basically as drives get larger the probability of hitting a read error during reconstruction increases and therefore you need to have more redundancy to deal with this. He suggests that as of 2009 drives […]

Some Notes on DRBD

DRBD is a system for replicating a block device across multiple systems. It’s most commonly used for having one system write to the DRBD block device such that all writes are written to a local disk and a remote disk. In the default configuration a write is not complete until it’s committed to disk locally […]

Hetzner Failover Konfiguration

The Wiki documenting how to configure IP failover for Hetzner servers [1] is closely tied to the Linux HA project [2]. This is OK if you want a Heartbeat cluster, but if you want manual failover or an automatic failover from some other form of script then it’s not useful. So I’ll provide the simplest […]

Why Clusters Usually Don’t Work

It’s widely regarded that to solve reliability problems you can just install a cluster. It’s quite obvious that if instead of having one system of a particular type you have multiple systems of that type and a cluster configured such that broken systems aren’t used then reliability will increase. Also in the case of routine […]

A Basic IPVS Configuration

I have just configured IPVS on a Xen server for load balancing between multiple virtual hosts. The benefit is not load balancing but management. With two virtual machines providing a service I can gracefully shut one down for maintenance and have the other take the load. When there are two machines providing a service a […]

Kernel Security vs Uptime

For best system security you want to apply kernel security patches ASAP. For an attacker gaining root access to a machine is often a two step process, the first step is to exploit a weakness in a non-root daemon or take over a user account, the second step is to compromise the kernel to gain […]