Debian Linux with a 3ware Escalade 8506 NOTE: See the updates below
I was recently asked to find a cheap Linux RAID box. After much research, I decided on the following system:
- Intel Pentium 4 2.8 GHz (~$260CDN)
- Intel MB SE7210TP1-E Entry-level Server board (~$200CDN)
- 3ware Escalade 8506-4LP Serial-ATA IDE RAID card (~$425CDN)
- 4x160GB Seagate SATA Hard Drives (4X~$189CDN)
- 3ware hot-swappable drive cage (4 drives in 3 5.25" slots)
Approximate prices are included. These prices were more or less accurate as of April 2004.
The trickiest piece of the puzzle was the RAID card. I did a lot of investigation. It turns out that I think I made the right choice. Here's a quick recap of what I learned about IDE RAID support in Linux:
- Promise cards are terrible. Even the high-end cards rely on a large software portion to work correctly. By all accounts, these cards a very nice to work with in Windows, and equally painful in Linux. They're a bit cheaper than the competition and have a great distribution channel and brand recognition. Because of this, they're everywhere. Every Linux admin I spoke with had been forced to work with a Promise card, every one of them cursed their barely-working binary-only drivers. Every one of them told me to stay away from Promise.
- Adaptec makes some IDE RAID cards. One admin I spoke with worked with one in early 2003, he had headaches with it, bit I don't recall the details. I couldn't find them anyway, so I skipped Adaptec
- Everyone said that they had heard good things about 3ware. I'd never heard of them before. I looked into it, their drivers are completely Open Source, and have been included in stock kernels since 2.2. The cards I was most interested in where the 7506 and 8506. These are 4-port P-ATA and S-ATA cards respectively. One excellent feature is that, from Linux's perspective, these controllers are the same. That is, the P-ATA driver works with the S-ATA controller. All differences are handled in hardware. Drivers for both have been around since 2.4.18.
- 3ware, and most other IDE RAID controllers show their drives as SCSI disks. The 3ware card handles the RAID array completely in hardware. My stock bootable Debian Woody CD with kernel 2.4.18 recognized the array as one big HD (/dev/sda1.)
- One caution I read about was that, because the drives show up as SCSI disks to Linux, you can't use hdparm to optimize the disk speed. I've read that this is particularly a problem with Promise cards. I've also read that the 3ware cards don't have this problem because optimization in done in hardware on the card.
- I was told by a long-time Linux admin to spend the extra $300CDN on the hot-swappable cage. I took his advice, time will tell if this was a good move.
My standard Debian Woody 2.4 boot CD saw the 500GB array as /dev/hda1, all is well. After the system was up and running I pulled one of the drives, there was slight pause but then everything kept chugging away. I replaced the drive and the card started rebuilding the array in the background. 3ware's software will optionally send out an e-mail when the array status changes, and the interface for the array is accessible over a website. Very slick.
I'm building a 2.4.26 kernel package as I write this, but all told the system seems pretty darn slick.
The total cost with a burner, case, floppy, 512MB RAM and an extended warranty: about $2500CDN. The system seems to work very well, 3ware's drivers were as solid as advertised, the software setup was easier than I would have imagined, and 3ware sees no problem with releasing their software as Open Source. So far we've purchased two 3ware cards. I'm certain we'll be buying more. 3ware as a company certainly gets my seal of approval.