To help make MariaDB better, simply add “plugin-load=feedback.so” to your my.cnf file! On Windows, add ”feedback=ON” to your my.ini file, or click the checkbox during the installation of the MSI package.

See http://kb.askmonty.org/en/user-feedback-plugin for more information.

I will teach pre-conference training sessions on the Friday at DDU:

• MySQL Query Design ($220 half-day)
• MySQL Server Tuning ($220 half-day)

The material is made specific to Drupal developers and users. The query design skills, for instance, will help you with module development and designing Drupal Views. The two half-days can also be booked as a MySQL Training Pack for $395.

On Saturday afternoon in the main conference, I have a session Scaling out your Drupal and Database Infrastructure, Affordably covering the topics of resilience, ease of maintenance, and scaling.

I’m honoured to have been selected to do these sessions, I know there were plenty of submissions from excellent speakers. As with all Drupal conferences, attendees also vote on which submissions they would like to see.

After DDU I’m travelling on to Ballarat for LinuxConfAU 2012, where I’m not speaking in the main program this year, but will have sessions in the “High Availability and Storage” and “Business of Open Source” miniconfs. I’ll do another post on the former – the latter is not related to Open Query.

See http://2011.osdc.com.au/SQLL for the talk abstract.

First of all, you may wonder why I bother with SATA disks at all for RAID. I’ve written about this before, but they simply deliver plenty for much less money. Higher RPM doesn’t necessarily help you for a db-related (random access) workload, and for tasks like backups which do have a lot of speed may not be a primary concern. SATA disks have a shorter command queue than SAS, so that means they might need to seek more – however a smart RAID controller would already arrange its I/O in such a way as to optimise that.

The particular application where I tripped over Green disks was a backup array using software RAID10. Yep, a cheap setup – the objective is to have lots of diskspace with resilience, and access speed is not a requirement.

Not all Green HDs are the same. Western Digital ones allow their settings to be changed, although that does need a DOS tool (just a bit of a pest using a USB stick with FreeDOS and the WD tool, but it’s doable), whereas Seagate has decided to restrict their Green models such that they don’t accept any APM commands and can’t change their configuration.

I’ve now replaced Seagates with (non-Green) Hitachi drives, and I’m told that Samsung disks are also ok.

So this is something to keep in mind when looking at SATA RAID arrays. I also think it might be a topic that the Linux software RAID code could address – if it were “Green HD aware” it could a) make sure that they don’t go to a state that is unacceptable, and b) be tolerant with their response time – this could be configurable. Obviously, some applications of RAID have higher demands than others, not all are the same.

What we do:help clients prevent problems (rather than being the fire department), we work on a subscription basis although we also do some ad-hoc consulting, and training. Apart from MySQL/MariaDB query and DBA work, we do quite a bit of system administration. Mainly Red Hat and Debian based distros, and expect to see replication and the MySQL-MMM multi-master system. You’d work from home, whereever it might be, so you will need to be self-motivating (but we do keep in touch online).

What we’re not: a full-time employer. With us, you make a life rather than a living. Everybody is contracted part-time. You can make enough to live comfortably, but that has nothing to do with hours. If you’re stressed about not filling all hours in your week with work-work-work, we’re not the company for you… there’s more to life than work, and we feel that’s really important.

Haven’t scared you off yet? Groovy. Take a peek at our jobs page for additional detail and contact info. Hope to hear from you!

So basically, the functions that do a “is this a strong password” should seriously reconsider their approach, particularly if they’re used to have the app decide whether to accept the password as “good enough” at all.

Update: Jeff Preshing has written an xkcd password generator. Users probably should choose their own four words, but it’s a nice example and a similar method could be used by an app to give “password suggestions” that are still safe.

However, I didn’t just remove the other stuff, because it can be very helpful in tracking down problems and putting misconceptions to rest. On SANs (and local RAID of course) you have things like block sizes and stripe sizes, and opinions on what might be faster. Interestingly, the real world doesn’t always agree with the opinions.

We Mark Callaghan correctly pointed out when I first published it, hdlatency does not provide anything new in terms of functionality, the db IO tests of sysbench cover it all. A key advantage of hdlatency is that it doesn’t have any dependencies, it’s a small single piece of C code that’ll compile on or can run on very minimalistic environments. We often don’t control what the base environment we have to work on is, so that’s why hdlatency was initially written. It’s just a quick little tool that does the job.

We find hdlatency particularly useful for comparing environments, primarily at the same client. For instance, the client might consider moving from one storage solution to another – well, in that case it’s useful to know whether we can expect an actual performance benefit.

The burst data rate (big sequential read or write) which often gets quoted for a SAN or even an individual disk is of little interest to database use, since its key performance bottleneck lies in random access I/O. The disk head(s) will need to move. So it’s important to get some real relevant numbers, rather than just go with magic vendor numbers that are not really relevant to you. Also, you can have a fast storage system attached via a slow interface, and consequentially the performance then will not be at all what you’d want to see. It can be quite bad.

To get an absolute baseline on what are sane numbers, run hdlatency also on a local desktop HD. This may seem odd, but you might well encounter storage systems that show a lower performance than that. ‘nuf said.

If you’re willing to share, I’d be quite interested in seeing some (–quick) output data from you – just make sure you tell what storage it is: type of interface, etc. Simply drop it in a comment to this post, so it can benefit more people. thanks

The lease costs are a bit steep, as is common these days… chances are we’ll just buy our next place.

Follow-Up yes this was an April 1st post. But, everything in the above post is the truth, it’s just phrased to be very open for a bit of mis-interpretation

I find that the real world provides plenty of fun and unbelievable yet true tidbits, so why bother making up nonsense!

> [...] tens of gigs of data in MySQL databases.
> Some in memory tables, some MyISAM, a fair bit InnoDB. According to my
> understanding, when one doesn’t have several hours to take a DB
> offline and do dbbackup, there was/is ibbackup from InnoBase.. but now
> that MySQL and InnoBase have both been ‘Oracle Enterprised’, said
> product is now restricted to MySQL Enterprise customers..
>
> Some quick searching has suggested Percona XtraBackup as a potential
> FOSS alternative.
> What backup techniques do people employ around these parts for backups
> of large mixed MySQL data sets where downtime *must* be minimised?
>
> Has your backup plan ever been put to the test?

You should put it to the test regularly, not just when it’s needed.
An untested backup is not really a backup, I think.

At Open Query we tend to use dual master setups with MMM, other replication slaves, mysqldump, and XtracBackup or LVM snapshots. It’s not just about having backups, but also about general resilience, maintenance options, and scalability. I’ll clarify:

• XtraBackup and LVM give you physical backups. that’s nice if you want to recover or clone a complete instance as-is. But if anything is wrong, it’ll be all stuffed (that is, you can sometimes recover InnoDB tablespaces and there are tools for it, but time may not be on your side). Note that LVM cannot snapshot between multiple volumes consistently, so if you have your InnoDB ibdata/IBD files and iblog files on separate spindles, using LVM is not suitable.

• mysqldump for logical (SQL) backups. Most if not all setups should have this. Even if the file(s) were to be corrupted, they’re still readable since it’s plain SQL. You can do partial restores, which is handy in some cases. It’ll be slower to load so having *only* an SQL dump of a larger dataset is not a good idea.

• some of the above backups can and should *also* be copied off-site. that’s for extra safety, but in terms of recovery speed it may not be optimal and should not be relied upon.

• having dual masters is for easier maintenance without scheduled outages, as well as resilience when for instance hardware breaks (and it does).

• slaves. You can even delay a slave (Maatkit has a tool for this), so that would give you a live correct image even in case of a user error, provided you get to it in time. Also, you want enough slack in your infra to be able to initialise a new slave off an existing one. Scaling up at a time when high load is already occurring can become painful if your infra is not prepared for it.

A key issue to consider is this… if the dataset is sufficiently large, and the online requirements high enough, you can’t afford to just have backups. Why? Because, how quickly can you deploy new suitable hardware, install OS, do restore, validate, put back online?

In many cases one or more aspects of the above list simply take too long, so my summary would be “then you don’t really have a backup”. Clients tend to argue with me on that, but only fairly briefly, until they see the point: if a restore takes longer than you can afford, that backup mechanism is unsuitable.

So, we use a combination of tools and approaches depending on needs, but in general terms we aim for keeping the overall environment online (individual machines can and will fail! relying on a magic box or SAN to not fail *will* get you bitten) to vastly reduce the instances where an actual restore is required.
Into that picture also comes using separate test/staging servers to not have developers stuff around on live servers (human error is an important cause of hassles).

In our training modules, we’ve combined the backups, recovery and replication topics as it’s clearly all intertwined and overlapping. Discussing backup techniques separate from replication and dual master setups makes no sense to us. It needs to be put in place with an overall vision.

Note that a SAN is not a backup strategy. And neither is replication on its own.