life as i know it

Expanding RAID & Partitions on Mac (part 2)

Scott — Sun, 06 Dec 2009 19:27:03 +0000

So I’ve been doing some thinking on why the mac has problems with expanded volumes. By expanded volumes, i mean a volume that gets bigger after initial creation. This isn’t an issue for physical disks, since their size is set. But virtual volumes, such as those presented by a RAID card can be “grown” through raid magical goodness.Once they’ve been grown - someone/something needs to update the GPT headers to say “this disk is much larger than before”. Part 1 accomplishes that through destroying the GPT headers, and re-creating them. It works, but man is it nerve-wracking.The other way one could do this, is by directly editing the GPT headers.In the GPT headers there are some fields:

FirstUsableLBA

The first usable logical block that may be used by a partition described by a GUID Partition Entry.

LastUsableLBA

The last usable logical block that may be used by a partition described by a GUID Partition Entry.

AlternateLBA

LBA address of the alternate GUID Partition Table Header.

HeaderCRC32

CRC32 checksum for the GUID Partition Table Header structure. This value is computed by setting this field to 0, and computing the 32-bit CRC for HeaderSize bytes.

What has to get updated is that LastUsableLBA and AlternateLBA. AlternateLBA should be = the last block on the hard drive.LastUsableLBA should be something like AlternateLBA-32.Once you’ve updated these, you have to calculate a new CRC32 checksum.If you’re a good person, you would go ahead and write the alternate header to the end of the disk - a bad person would just let the OS panic about the lack of backup headers and fix it itself.I’ll be doing some testing of this over the coming weeks, and i’ll let you know what i find.

Never enough storage

Scott — Sun, 06 Dec 2009 05:23:17 +0000

Why is there never enough storage available? The 13TB array keeps on getting full - so time to build Array2. I should name my arrays - got suggestions?Anyways, I want Array2 to be a little less hacked together than Array1. So, my choices for enclosure include:

Norco RPC-4220 $362 shipped from MWave
- 4U (19″ x 25″ x 7″)
- 20 Hot Swap SAS/SATA bays
- Five internal SFF-8087 Mini SAS connectors
Norco RPC-3216 $346 shipped from MWave
- 3U (19″ x 25″ x 5.1″)
- 16 Hot Swap SAS/SATA bays
- Four internal SFF-8087 Mini SAS connectors

These are nice enclosures, but you also need a power supply($100ish), power supply controller, and a sas expander ($250). So you’re really looking at $750 ish.Supermicro (who makes the drive bays in Array1), makes some nice enclosures.

SC936E1 $1029 or $64/bay
- 16 hot swap bays in 3U
SC933E1 $942
- 15 hot swap bays in 3U
SC836E1 $1010
- 16 hot swap bays in 3U
SC846E1 $1180 or $49/bay
- 24 hot swap bays in 4U

Yes, the supermicro cases are spendy. But - they include the power supply and sas expander. And they’re great quality.My only bitch is with the depth of the cases. I don’t need space to put a motherboard in the case, so something 25″ deep is just…. overkill.PS: With any case that doesn’t have a motherboard in it, you can use the Supermicro CSE-PTJBOD-CB1 to control the power supply. It’s $25 well spent.

Expanding RAID & Partitions on Mac

Scott — Wed, 22 Apr 2009 22:17:07 +0000

Once my raid array had finished upsizing from 5.5GB to 9.1GB, I had to resize the partition in order to actually use the space. OS X’s Disk Utility gives the oh so friendly error (Partition failed with the error: MediaKit reports partition (map) too small. ) Not particularly helpful, is it. All my googling has never found an answer, so I thought I’d post my solution here.

Open up a terminal
run ‘df’
Note the mount point for the drive you’re trying to expand. Mine was “/dev/disk4s1″. We’re only interested in the disk, not the slice, so I’m going to use “/dev/disk4″.
In Disk Utility, unmount the current partition on the disk.
run “sudo gpt show /dev/disk4″. If this fails, you probably didn’t unmount the partition first.
The line with the largest size is the partition we care about.
In Disk Utility, unmount the partition again.
run “sudo gpt destroy /dev/disk4″
run “sudo gpt create -f /dev/disk4″
run “sudo gpt add -b 409640 -s 11719262168 /dev/disk4″. Notice those numbers came from the start and length of the partition we want to save.
Reboot.
Now use Disk Utility to resize the partition. If you didn’t reboot, Disk Utility will probably give an error, but it might still work. Reboot now anyways.

Basically what’s going on here is that the GPT table is built only big enough for the drive it’s on. That’s a logical assumption - hard drives don’t magically get larger - unless they’re RAID arrays. We’re just removing the GPT partition information, and replacing it. Should things go crazy, as long as you’ve got the start and size information for the partition you care about, you should be good. No guarantees obviously, but I’ve done this three times and no data loss yet.

New Sink!

Scott — Mon, 30 Mar 2009 13:49:34 +0000

Finally replaced the horrible old sink in my bathroom. One of these days I’ll remember to take a “before” picture as well. The new sink is a good 5 inches wider, but not as deep, so the bathroom actually feels bigger with it.

Only bad thing was my old faucet (A Price-Pfister Portland) doesn’t fit. side note: Price-Pfister makes nice faucets. Their web site designer/maintainer should be shot. Their “product finder” doesn’t.

SAS Cables

Scott — Sat, 21 Mar 2009 18:59:01 +0000

Searching for cheap sas cables….

1M SFF-8088 to SFF-8088 cable

.5M SFF-8087(host) to 4 SATA(device)

SFF-8087 to SFF-8088 Adapter

All pricing is as of 3/21/2009

Update! PC-Pitstop will match the $15 SAS breakout cable price if you ask.

Goodbye stump, hello concrete!

Scott — Fri, 20 Mar 2009 23:17:40 +0000

There once was a bad tree.It had to go. So I played arborist with a chainsaw, and there was nothing but a stump left. anyways - that stump was there for ages. It had chain link fence in it, so i couldn’t just use the chainsaw on it. (seen here in a pic from 2007)Fast forward a couple years. I got the great idea to move the back fence in a bit, and carve out a place for the trash cans to sit where they would be on my property, but accessible to the trash men. How do you remove a stump? Kerosene. Charcoal briquettes, and scrap wood to burn as a fuel source. After a couple weeks of lighting everything on fire every night - the stump was gone. So I poured the concrete, laid the brick pavers on top - and voila! The classiest trash can pad in the neighborhood.