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Month: October 2011

So long Notepad++, and thanks for all the chmod +x

Published on October 31, 2011

Just as soon as I post about changing from Notepad2 to Notepad++ I’m changing back as I’ve discovered an annoying issue where editing a Linux shell script with executable permissions over a samba share, removes the executable permissions.

What I can’t figure out is why it’s only removing the user’s execute permission. I had thought perhaps it was deleting and recreating the file, which would cause the share’s create mask to remove execute permissions, but that’s not it. If a file is set 0775, it will become 0655 after a save.

I may have a workaround for it in a few days, but for now I’m back to using notepad2 for my editing needs.

Replacing Notepad with Notepad++ using Image File Execution Options

Published on October 30, 2011

I’ve been irritated for sometime by the apparent lack of desktop real estate when working on many webdev tasks in Windows 7. It may have been the same in WinXP, but honestly it’s been so long I don’t remember. While I don’t profess to be a greybeard or anything like that, I’ve yet to find an IDE that makes my life easier when working on PHP, JS, and CSS especially when most of the time I’m not doing much more than quick fixes.

For the longest time my solution to my conundrum has been to use Notepad2, actually a modified version of it Notepad2 w/ code folding. What I’ve noticed, and what’s prompted me to move away from Notepad2 is that the lack of tabs means that many times I’ll have a half dozen windows open as I try and find and fix whatever craziness I’m working on, and that was a large part of my lack of screen real estate.

My solution was, rather drastically, to dump Notepad2 and move to Notepad++. Unfortunately that brings it’s own issues to the table. The big one, and what prompted this post, is that Notepad++ doesn’t cleanly replace notepad completely. What you can do is have it take over the file extensions for the files you want it to edit. That of course brings it’s own set of problem, namely now your file types all read “Notepad++ file” instead of something more useful like what it actually is.

The best non-destructive way to replace Notepad is to use the Image File Execution Options hook in the registry to have windows launch Notepad++ instead of Notepad. The trick, unlike Notepad2 is that Notepad++ wasn’t apparently designed to be pluged in this way directly. There is a nice, article in the Notepad++ wiki on replacing notepad and that’s what brings me to this post.

The problem I’ve run into is that following their instructions it’s impossible to edit files with either spaces in their name or spaces in the path name. The procedure is the same as outlined by the Notepad++ wiki, only there’s a slight modification to the script that’s used. The the modified script is shown below.

Option Explicit
Dim sCmd, x, arg
sCmd = """" & LeftB(WScript.ScriptFullName, LenB(WScript.ScriptFullName) _
		- LenB(WScript.ScriptName)) _
		& "notepad++.exe" & """"
For x = 1 To WScript.Arguments.Count - 1
	arg = arg & " " & WScript.Arguments( x )
Next
sCmd = sCmd & " """ & trim(arg) & """"
CreateObject("WScript.Shell").Run sCmd, 1, True
WScript.Quit

Note: I’ve split the first sCmd line to make it fit on the page, the splits should work as well in the actual vbs file.

The key here is that script needs to collapse the file name arguments into a single quoted argument, which is what the for loop does now.

Hide from Sendto Menu

Published on October 30, 2011

So the last time I posted I mentioned that you can quickly get to the sendto folder, to say add some shortcuts to it, by typing shell:sendto into the address bar in Explorer or from the Type to Search box in the Windows start menu. Today’s handy tip comes from wanting to remove something from the sendto without making it hugely difficult to recreate it if I so desired.

So to hide something from the sendto menu without deleting it from the sendto folder, simply open up it’s properties (right click -> properties) and check the Hide box. Easy as pie.

Reminders: So many, so frustrating.

Published on October 18, 2011

Todo lists, tasks, reminders, whatever you want to call them I’m starting to think the correct name is pain in the asses. I currently have 5 completely incompatible implementations of tasks/reminders from 3 different providers, that don’t do me a bit of good since they can’t be synchronized between them.

First, there’s Tasks, in Mozilla Thunderbird/Lightning. It’s great that the Mozilla foundation though that a task list was worthwhile to include the only problem is no service seems to exist that they can be synced with. It won’t even let me create/sync them with the newish tasks feature that Google has added to Gmail/Google Apps for Domains.

Which brings us to Google’s tasks, long awaited and requested they finally got around to implementing them. Only catch is there doesn’t appear to be a way to synchronize them to something outside of Gmail, no support in Thunderbird, no way to get them on my phone. Maybe there’s better support if you’re on an android phone, but that has it’s issues as well.

Finally we have iCloud and Reminders, added to Apple’s iOS 5. Again, there’s no way to sync them (at least as far as I can tell) to a desktop client (at least not a Windows one), or for that matter get them out of iCloud. They sync between my phone and iCloud, I can edit and creat them from my browser though iCloud.com, but is that really ideal? Not to me. They do have a number of really cool features though, like the location based stuff.

NIH (not invented here) syndrome is driving me up a wall, why there isn’t a simple universally agreed upon standard for communicating tasks/reminders between various desktop and mobile devices. I shouldn’t have to fire up iCloud to add a task that I could have added while I was in Thunderbird replying to an email.

The more things go towards being digital, and especially in the cloud, the less they seem to be able to work well together. This, I think, needs to be fixed sooner rather than later, as it stands it’s just driving me up a wall.

Finally Done with this RAID project…

Published on October 7, 2011

Three days of screwing around and as far as I can tell I’ve successfully moved all my data from one array to another while keeping the machine and data online the whole time–other than the few minutes of reboots to remove and replace hardware. Not bad for a SOHO file & web devel server.

Expanding things…

After the move was completed, and the array was re-syncing I expanded the LVM logical volume and the file system inside of it. Expanding the LV was simple and fast using lvextend (8) and the following command…

root@host:# lvextend data /dev/md#

It should take a couple of seconds while it allocates the new extents and returns and that’s done.

Expanding the ext4 FS takes a bit longer, but as long as it’s being extended and not contracted, it can be done while the FS is online and mounted.

root@host:# resize2fs /file/system/mount/point

Adding the -P to resize2fs (8) would be handy, if it works I didn’t try it, adding progress information as the resize is done.

/dev/md127, wtf?

Rebooting to remove the old, now archival, hard drive and bringing the system back up raised an interesting head scratcher. The MD device that should have come up as MD0, came up as MD127. The /etc/mdadm.conf file looked correct, but it wasn’t putting the device where it should have been in /dev. The fix seems to be rebuilding the intiramfs…

root@host:# update-initramfs -u

With that done and a reboot the md device shows up as md0 like it’s suppose to.

Additionally md apparently now supports assigning arrays descriptive names, like "hostname:1" and the array shows up under /dev/md/ as that name in addition to the regular /dev/md* device.

A note on the Hitachi 5k3000s

I went with these drives based on this post on the Backblaze blog. Well, with the caveat that I’m still leery of 3TB drives, so I’m using 2TB drives. I don’t even think that the board or the SATA controllers I have in this box support >2TB drives (though the update later this month will).

More interestingly, the Hitachi 5k3000s are 512-byte sector drives, not 4K sector “advance format” drives. While the 4K sectors do have advantages on large drives in terms of insuring data integrity they also become somewhat fun trying to partition and align around. Partitions have to aligned to 4K boundaries (fdisk, as well as Windows’ partition tools, align to 1M (2048- 512-byte sectors) when DOS compatibility mode is disabled), on top of that you have to be careful where the MD device places the metadata information, as that can shift the FS alignment as well. And for that matter, I have no idea what kind of overhead LVM adds in terms of alignment. In short, 4K drives are, IMO, still something of a mess, and probably will be fore sometime.

One nice thing is I’m seeing about 2x the performance of these Hitachi drives than I was with WD Greens, even though I believe they were properly aligned. Benchmarks show the drives I have can do 140MB/s on the other tracks, I don’t get that yet, but I’m hopeful that a new system with a faster CPU (Xeon E3-1220) and more modern SATA controllers (not the ancient SiI3114 on this Tyan Thunder K8W) will get me closer to that.

The Brass Tacks: What I learned

  • madam’s support for RAID 10 is lacking compared to all the other levels
  • LVM, especially pvmove (8) was more useful than just having a realizable volumes.
  • Planning storage, especially growth is a pain in the rear, when you can’t just throw a ton of disks at it

Breaking Arrays, Moving Data, LVM Good for something

Published on October 6, 2011

Who knew LVM would be good for something. Well, maybe, I’ll know for sure sometime tomorrow, or late tonight, if it works it’ll be great, if it doesn’t. I’ll be damn glad I backed up these drives.

Yeah, so back to LVM. I always wondered if creating an LVM volume over the top of an MD raid volume was a good idea or if it wasn’t just adding extra overhead. And EXT4 partition can be extended without the help of LVM and so can an MD raid device. So why add the extra layer in there.

pvmove

That’s why.

Breaking Arrays, Making Arrays

Wanting to avoid the “blow it away and restore from backup” strategy, especially since WD Caviar Greens are so damn slow compared to just about everything else, I decided the best course of action would be to split the existing unresizable md array and create a new second one. Something like….

mdadm /dev/md0 --fail /dev/sdb1
mdadm /dev/md0 --remove /dev/sdb1
mdadm --create /dev/md1 --level=1 --raid-devices /dev/sdb1 missing

The end result, 2 degraded but fully functional md arrays. One still hosting the data volume group with my home logical volume, and one with a big empty disk.

The trick now is to move the data.

LVM Really is Good for Something

The question of how to move the data stumped me for a bit. I could create a new volume group (VG), or at least a new logical volume in the same data VG I already had, format it, and rsync the data across. Of course then I would have to edit at least my /etc/fstab and to get things pointed to the right place. The alternative that came up as I was digging though the LVM documentation is a nifty function called pvmove (8) that will move the physical extents of an LVM from one physical drive to another in a volume group (or to multiple drives in a volume group if needed). Moreover, as best as I can interpret the docs, it does this in a way that’s safe to do with the system online.

All told, for my system, the process looked something like this…

vgextend data /dev/md1
pvmove /dev/md0 /dev/md1

Now it’s back to the waiting game. It’ll be 5 or 6 hours before the pvmove is complete, then I have to tear down the md0 raid array and add the /dev/sdd device that’s left in md0 to md1. That will necessitate a 6, or so, hour re-sync. After which, I’ll reboot, make sure md1 becomes md0 and everything is found properly. Then it should hopefully be a short task of expanding the logical volume from 1.5TB to 2TB and then the EXT4 file-system inside of it. If not, well I’ll be damn glad I made that 6-hour long backup, wont I?

MD, RAID10, ARRRRRrrrrrrgggghhhh!!!!

Published on October 6, 2011

Normally the complexity of doing something in Linux doesn’t bother me. Arcane and convoluted commands don’t scare me, they never really have; they just take some getting use to. The problem I have is when the command, or the underlying system is only half implemented.

My current project has been replacing a pair of 1.5TB WD Caviar Greens with 2TB Hitachi 5k3000s. Yes I see the irony in replacing WD drives with drives made by a company that just sold their drive division to WD. On the up side 500GB more space nets me enough space to backup the rest of the computers on the network and still have as much free space as I had before, which was running down anyway; oh and the Hitachi’s are faster too.

Replacing the drives in the RAID array has gone smoothly enough using the following procedure:

  1. Fail the disk to remove using mdadm /dev/md0 --fail /dev/sdX#
  2. Remove the disk from the array using mdadm /dev/md0 --remove /dev/sdX#
  3. Power down the machine (hot swap is coming in a future upgrade)
  4. Swap the physical drives
  5. Bring the machine back up
  6. Add the new drive to the array using mdadm /dev/md0 --add /dev/sdX#
  7. Let it re-sync.

I’ve done this for 2 1.5TB Greens, one that was failing and one that’s now going to become a proper backup target.

Now that I have two 2TB drives in there, I want to use them, and that means extending the md group to the full size of the array. So far as I can tell, that should be a simple…

mdadm -G /dev/md0 --size=max

…but, apparently that’s not the case if the array is configured as RAID10. RAID10, which gives the performance of RAID0 with redundancy of being able to lose a disk, which IMO is perfect for slow 5K RPM disks. MD even has a nice feature where the RAID10 array can be created in a partial 2-disk configuration then extended to the full 4+ disk configuration later. In the “partial” mode, it behaves exactly like a RAID-1 array.

Which brings me to the meat of this rant. I can re-size a RAID1 array, I can convert a RAID 1 array to 5, 6, or even 0. However, mdadm can’t re-size a RAID10 array, even if it’s running in what amounts to RAID1 mode, or convert it to RAID1 or any other RAID level for that matter.

Sigh…

Now it’s off to back up the damn thing, kill it rebuild it, and restore everything…. At least I’ll know if my backup procedure works.

Wordpress is a Pig and Dreamhost’s VPSes aren’t configured for it.

Published on October 5, 2011

I’ve been fighting with this for quite sometime. I moved to a VPS over a year ago in hopes of a more stable Dreamhost experience, and for a while it was. Then about 9 months ago my site started crashing in out of the blue. I’d be chugging along just fine then, “blam!”, site down. I started aggressively caching things with WP Super Cache, then W3 Total Cache. It helped a little, but ultimately things just got more and more unstable. About 2 months ago I gave up on using PhpMyAdmin when I needed to do SQL stuff, simply because it was an instacrash for my VPS. About 3 weeks ago, I had enough and decided it was time to seriously track down the problem.

To make a long story short, Wordpress, is a massive memory hog. I’m pushing on average 30MB before I even start loading plugins. That’s not a lot if you have a 8GB server dedicated to nothing but pushing wordpress but, 30MB is 5-10% of a small VPS. I’ve gone though all the Wordpress tuning guides I can find. I’ve manually cleaned up the database. Nothing really helps. Of course if the server was configured for the load it has, the problem would be considerably smaller.

Which brings us back to Dreamhost’s VPS. They say it’s designed to scale with the RAM that’s allocated to it. Sure, maybe if you’re running static HTML pages. In which case the 69 concurrent clients configured on a 400MB server would get ~6MB a piece which is just barely enough for Apache to serve static HTML. Even then it doesn’t really work out, since there’s non Apache overhead. In fact, now that I think about it, by default under full load, Apache is configured in such a way that it can easily exceed a VPS’s memory allotment just serving static content. 😮

Then comes mod_fcgi. By default it’s configured to allow 20 instances per process class (I’ll come back to this), and the Apache default is 1000.

What are process classes and why are they important. Process classes are spawned by the same executable and share a common virtual host and identity. For example, if my virtual host for cult-of-tech spawns a CGI process, that process can’t be used by another virtual host on my server. Now here’s the kicker. When wordpress gets going and everything is loaded, that 30MB+ of Wordpress and all the PHP overhead + whatever space you allot for caching (XCacahe, APC) is how big the fcgi istance will be. In my case, that means each php.cgi instance is 60-70MB. On a 400MB server, that means once you spawn 5-6 php processes you’ve used up the entirety of your VPS’s memory and, again, blam!

The kicker though, is Dreamhost’s overly aggressive memory manager on their VPSes. Instead of killing off processes, or for that matter special casing it and just restarting Apache if it’s running, the watchdog merely kills off the VPS. Well it may do more, because it can take 10 minutes for the VPS to come back up unless you manually reboot it.

Interestingly enough the answer to all of this is not to simply throw money at it. In the process of troubleshooting this I temporary pushed my memory limits up, and even at 600MB or 800MB the config would still allow enough processes to cause the server to crash. For that matter my development server, which has a ton of RAM available, can comfortably do many of the things that was causing my VPS to crash, without exceeding a 200MB memory foot print.

Simply put, there’s no reason a lightly trafficked Wordpress site should require more than 300MB, maybe 400MB, but certainly not 600MB to simply stay upright. At least not with a properly configured server behind it.

The moral of the story is:

  • Wordpress is a memory pig, and they need to seriously consider a couple of releases focusing entirely on performance and lowering the memory footprint.
  • Dreamhost’s configuration for Apache and mod_fcgi on their VPSes is overly generous for small servers and needs to be curtailed to more reasonable numbers.
  • Dreamhost’s VPS memory watch dog is aggressive, and naive, and will take down a server in a hard to quickly recover way to insure it doesn’t use more resources than the client is paying for.

And what am I doing about this?

I’ve curtailed my Apache and mod_fcgi configs to more reasonable settings.

I’ve set mod_fcgi’s MaxProcesses directive to floor( (400 - typical_process_size) / typical_process size) and my Apache MaxClients to floor(((typ-cgi-process size * 2) - 20) /5). I won’t be anymore specific than that, because what will actually work while still being performant, varies based on site, software, traffic, caching, and number of virtual hosts.