A couple of months ago, while replacing the power supply in my workstation, I managed to drop my system hard drive onto a concrete floor. From that time on, that drive has sounded different in my system.

Now, a couple of months later, I am seeing the onset of I/O errors in the drive. Apparently I damaged it and it is beginning to deteriorate.

So, I need a new system hard drive.

I run SCSI drives, and the drive I damaged is an IBM Ultrastar-320 15K drive. Very nice, very fast, and has been very reliable.

But, parallel SCSI has "hit the wall" and it would appear clear that soon it will be left in the dustbin of history, replaced by faster serial interfaces.

So, I am not sure that I should purchase a replacement SCSI drive.

My requirements for hard drives are (in order) 1. reliability; 2. performance; 3. cost. Given this priority list, you can see that I won't consider PATA or desktop SATA drives for my system. They are cheap but lack both reliability and performance in stressed situations.

So, my choices are either a new SCSI drive, an SAS drive, or an enterprise-grade SATA drive. If I purchase either of the latter two, I also need to purchase a controller. This raises the price considerably, but positions me for the future, while purchasing a new SCSI drive explicitly doesn't position me for the future.

If I purchase a controller, it would be plugged into a PCI bus; my motherboard is too old to support PCI-E.

Also, I have 4 SCSI drives in this box (no RAID; I just always would stick another drive in when I needed more space) and if I replace the system drive with another technology, I will then have 3 SCSI drives and one of another technology in the system.

SAS is very, very expensive, and I am not sure that it provides much advantage over enterprise-grade SATA (something like the WD Raptor drives).

I would be interested in comments from people here who are using any combination of these three technologies (SAS, E-SATA, SCSI) and I would very much like to know what you think the best choices might be, given my goals and current constraints.

I suggest go with Western Digital 'Raptor' series. If you want a lot of capacity, similar performance (low latency), and at a lower noise level Hitachi A7K1000. If you want ultra performance and do not mind paying a very, very premium price tag, Bitmicro E-Disk SSD hard drives can be used. Your workstation will fly through your programs.

I never have any problems with IDE because I use a very reliable controllers from Highpoint. They work in a wide variety of OS and they are robust. After seven years of use, they have not failed once even when I did something foolish by removing the hard drive while the computer is on. They can handle constant video capturing and in a hot environment greater than 85 degrees F, so it can handle stress very well.

There are SCSI to SATA converters, but they are compatible with some SCSI controllers.

Hard drives are not reliable, so finding the most reliable hard drive is pointless. Hard drives fails, so just pick anything and back up. The hard drive brands that I use are Hitachi or Western Digital. If you are going for reliability, I recommend setup either RAID-5 or RAID-6 with a hot spare. A hardware RAID controller such as from 3ware could be used in your setup.

SATA is out pacing SCSI. SATA-II came out and SCSI is now playing catch up. About 80 hard drives can be connected to a 3ware SATA-II controller because of the port multipliers.

SAS is a hybrid controller because it can handle either SCSI or SATA. It is usually used in huge file servers or used as a back up server. SAS does not have many brands competing against each other, so the price will stay high and rarely come down in price. I have not seen a SAS controller in stores.

Interesting. I suppose the controller reorders requests to minimize head motion? Since 1990, I have had exactly one SCSI hard drive fail (exclusive of this current failure which I am sure I induced), and this is out of dozens I have had in service 24/7/365. The usual pattern was that after several years I would cycle the machine out of service due to it becoming obsolete, and sometimes I'd move the hard drive to some other machine. These were machines used in my office. I have one 9.1 Gig Quantum in my workstation which has been in continuous service since 1995.

Over the same period of time, literally every IDE drive I have had has failed. The only exceptions to that are the new PATA drive I installed in my laptop last spring (to replace a failure) and a Seagate drive that I picked real cheap up last spring and stuck into a Vantec USB case to give me portable drive. Both of these, being new, haven't yet failed.

As I say, I have found SCSI drives to be quite reliable mechanically and electrically. They have heavier, stiffer cases than IDE drives, are more vibration resistant, use smarter electronics to control the transfer, have better thermal management, and generally just hold up better - though dropping on a concrete floor is still not recommended.

Of course, backing up is still the key to preserving data.

WD advertises the Raptors as being of similar quality to SCSI but with a SATA interface. Is the same true of these other two series?

The Western Digital 'Raptor' series uses surplus SCSI hard drives. Now, I do not know although could be equal quality since the parts are an old SCSI model, but with different electronics. Western Digital is a lot better than Seagate.

I have an IBM 74GXP 20 GiB hard drive that is lasting seven years and more from all the abuse. This series has a reputable of failing.

Western Digital and Hitachi is resilient to poor power quality. Seagate and Maxtor are pathetic.

Over time hard drive manufactures improves their firmware, so the latest models gets more efficient than previous models and provide new features. Some hard drive manufactures use IDE hard drives as a test ground for new features.

Vibrations is caused by the RPM of the hard drive. If the hard drive RPM is 15000, it will vibrate a lot and produce a lot of heat. RPM rarely shows performance of the hard drive. Hitachi or IBM always shows that with an optimized firmware on a low RPM hard drive, it can provide lower latency and similar performance to hard drives with higher RPM. Lower latency comes at a cost of lower throughput which can always be increased with an array of hard drives in striped mode.

I am not sure what kind of loads you put on your hard drives. Also how much you abuse your hard drives when handling and mounting them.

I had a hard drive that partially failed. The sectors got corrupted and I used a utility to re-allocate the sectors to known good ones. The drive then worked, but is not efficient anymore. I then replaced it (IBM 60GXP) with Western Digital RE series.

I suggest run Spinrite every month to make sure the drive is ok and it is not doing too much ECC and to check any hidden S.M.A.R.T logs.