You have some old disks. Are they best reused as disks or recycled as metal? Here are guidelines based on practical experience. We look at age, capacity, use, and technology generations.
Who?
People with old disks left over from upgrades or disks in computers you no longer use have an opportunity to make use of those disks instead of just crushing them as scrap metal. Most people with disks do not know what to look at while when deciding on reuse.
You could look in forums for advice often from people who have limited experience or live in countries where the cost is completely different. Even worse, you could look in Reddit or ask an AI, an Artificial Idiot clump of software that will just merge test from unknown sources. You need advice from someone with the same disks, extensive experience with disks, and a similar usage.
To know your disk, you need to read the physical label or use a disk information program to give all the details or, if you have the exact model number, you can look up the specifications at the manufacturers Web site. There are only a few technical specifications you need to understand.
When?
Disks less than three years old are most likely in the original computer and the computer is not yet ready for recycling. Computers are often dumped by companies after three or five years. The disks may them be available for reuse.
Disks more than three years old are hard to reuse unless you know something about the disks and the ways to reuse disks and your plans for the next few years. As an example, there is no point in reusing a small disk if you are expanding from photographs to videos. Videos use a mass of space. You would waste time and resources on reusing the small disk then have to replace it.
There are disks available from upgrades. You computer might arrive with a 500 GB disk then your file collection expands to 600 GB. Upgrade. Now you have a spare 500 GB disk and it is too small to use as a backup for the new 1 TB disk. Decision time.
I suggest planning disk upgrades for one to two years ahead as the upgrade process is a waste of time and one big upgrade is better than several small upgrades. My notebook was expanded from 256 GB to 1 TB instead of 512 GB as that saved one upgrade. Recently I jumped the notebook up to 2 TB before the 1 TB was full as I found a superb 2 TB SSD on sale.
Is your disk 80% or 90% full? This is another time to upgrade. My 1 TB notebook approached 80% full. Based on experience with other computers, the Windows OS starts to slow down at 80% full and the Linux OS drops into panic mode at 90%. Every other operating system and file system has a similar problem. Plan your next upgrade before hitting 80% full.
Where?
Your country will determine the cost of replacements and in many countries, most options are too expensive. You are more likely to leave the disk in the original computer and run both until they break.
My advice is based on Australia where hardware costs enough to think about everything carefully but is not expensive to the point of eliminating all alternative uses.
City or country? Magnetic disks do not like rough handling. Replace with SSD where there are lots of bumpy trips on primitive roads.
Why?
A good disk is too valuable to throw away and you might have to spend money to reuse it. Perhaps you have to buy a USB enclosure to reuse a disk as a backup. Weigh up the cost and benefit. Add in a comparison to buying alternatives.
Way?
Look at the brand, model, age, and use. If any are bad, or might be going bad in the next year, crush the disk. Your time is too valuable to waste on fitting old disks in new systems if they are going to fail within two years.
Hitachi, Seagate, Toshiba, and Western Digital are the good brands I see in used machines. There were other brands and they disappeared for a reason. I see forum posts warning you to never buy Seagate or Western Digital but they are usually based on a bad model. Both brands have multiple factories and had bad models or batches. In both cases, if the disk survives a year of use, it is a good model or batch.
Look carefully at the model number, the long detailed one , not the short glossy text. For magnetic disks, the big problem is a rubbish idea called SMR. Check the disk is CMR. If the disk is SMR, toss the disk in the metal recycling bin. You may have to visit the manufacturers Web site to find out which model is what.
In SSDs, the equivalent is QLC. Some new QLC SSDs might be ok but any old QLC is bad news. Junk it.
Age? Some good old disks were designed to last 10 years while others were cheap and designed to last only 5 years or less. If you have disks from about 5 to 15 years old, they might be one of the cheap options. You would have to check the model, the specifications for wear and the original guarantee. Toss out any disk where the guarantee was only one or two years.
Magnetic disks have bearings that wear out through use, will fail fast if run in a hot environment, and will deteriorate in storage. A disk might last 20 years in constant mild use within airconditioned luxury. The same disk can fail the first hot Australian summer without artificially cooled air. Do you know the history of the disk? I toss out anything I cannot verify.
I throw out unknown brands, unknown models, and disks with unknown history. I am keeping several good 7200 rpm CMR 3.5 inch disks up to ten years old because I know their history. They were not abused by hot summers. They were used for significant periods as 24/7 servers but the actual workload was not constant, mostly just daytime and mostly for once per day backups. Plus the replacement SSDs are too expensive.
Worth?
The disks I am keeping cost $300 or more new and one is just two years old. An SSD replacement is currently close to $400. I could reuse my disks for another year or three while 4 TB SSD costs drop.
The disks are in an old desktop computer not worth keeping. A good brand of powered USB enclosure for each disk is AU$25. I can spend $25 to reused them as USB backups instead of spending $400 for a new backup disk.
There are 4 TB USB disks under $400 but they are SMR, something I refuse to buy because SMR costs too much time. The cheapest SSD options can run fast in benchmarks but only for the trivial time needed for most benchmarks then they slow down to an SMR style crawl. My time is too valuable.
SSDs are better value when on the road where the bouncing around can kill magnetic disks. I will keep magnetic disks only for safe stable use on a shelf in my office.
What?
CMR
Disks are CMR, Conventional Magnetic Recording, or SMR, Shingled Magnetic Recording. SMR is painfully slow at random times. A backup starts as a 30 minute job then runs for 12 hours. Check the model number. Reject all SMR disks.
3.5 inch magnetic disks
2.5 inch or 3.5 inch magnetic disk? All new 2.5 inch disks are SMR so reject them. I have a beautiful old Hitachi 1 TB CMR 2.5 inch disk that is way faster than any modern 2.5 inch magnetic disk. I also have excellent 1 TB NVMe SSDs left over from upgrades to 2 TB. I can no longer justify using the 1 TB magnetic disk for anything as I have the NVMe SSDs for free, or the cost of a USB enclosure, which is about the same cost as a 2.5 inch USB enclosure. I will donate the 1 TB magnetic disk to a local technology charity and let them decide.
My 3.5 inch disks survive because 4 TB SSDs are still a premium product. Replace 1 TB and 2 TB 3.5 inch SSDs because the replacements are cheap and so much faster, you may be able to defer upgrading your computer for a year or two. When you hit 4 TB, you are balancing the speed of the magnetic disk against the falling price of 4 TB SSDs.
The 4 TB SSD cost is dropping as brands introduce 8 TB models. One day I will replace all the 4 TB magnetic disks with SSDs. For now, the magnetic disks are perfect for backup in a stable bump free office environment. Their long term sequential write speed is better than most affordable 4 TB SSDs after you fill up the small SSD pSLC cache.
SSD generations
The new generation of NVMe disks for use in USB enclosures includes the Crucial T500 which uses 40% less power than the previous generation from the same supplier. Crucial is the retail brand of Micron and uses the best of the Micron chips. There is a stupendously fast Crucial T705 but the T705 is way faster than any current USB option. The T500 can run USB 4 at maximum speed.
Given the long life of SSDs and the small cost difference between the T500 and the cheaper options, I could put a T500 in a USB 10 Gbps enclosure this year then move it up to a USB 4 enclosure when USB 4 enclosures are affordable.
This is part of the problem with recommending stuff. The T500 2 TB was to expensive to recommend then a few months after introduction, the price dropped like the temperature of Chilli condiments when you use Cayenne instead of Habenero.
Specifications
One measurement of good magnetic disk design is maximum stop/starts they survive. Those starts wear out the bearings extra fast. Not relevant for 27/7 on servers but it is still an indicator of reliability. My oldest disk was designed for 50,000 starts. My best recent disk is designed for 300,000 starts. The best of the 50,000 start disks lasted 5 years in desktop use. I would not keep them any longer.
One disk designed for many more starts lasted 11 years as a desktop because every part of the design and manufacture was way better than the best of the 50,000 starts disks.
Guarantee
What was the manufacturers guarantee? The ones with one or two years rarely lasted longer and should be scrapped immediately. In a good environment, the more expensive models with longer guarantees often lasted many years after the guarantee ran out.
SATA III
Is the disk older than SATA III? SATA III has a speed compatible with USB 3. Toss out disks limited to SATA II or SATA I as they are just to slow for any use.
USB enclosures
You can get USB enclosures for any old disk. USB 3 is similar in speed to SATA III but USB 3 is a sloppy standard and many USB 3 products are poor quality conversions of USB 2 technology.
USB 3.1 is a big rewrite of the USB 3 standard to fix all the errors in the USB 3 standard. USB 3.1 Gen 1 is the same speed as USB 3 but way more reliable.
Many USB "3" ports on computers are actually USB 3.1 Gen 2 which is double the speed or 10 Gbps, the fastest speed you can get through a USB Type A plug. USB 3.1 Gen 2 enclosures cost no more then Gen 1 enclosures as they can use mostly the same copper and silicon. When you buy anything with a USB Type A plug or socket, make sure it is 10 Gbps Gen 2. 10 Gbps gives a slight extra speed for SATA III as it can handle the full 6 Gbps.
USB 3.2 is almost the same cost and can deliver a slightly better 10 Gbps plus may have Gen 2*2 which is 20 Gbps. 20 Gbps is of no advantage for SATA III disks. The 20 Gbps would be an advantage if running a hub with two SATA III disks plugged in.
USB 4 with 40 Gbps is the next step up and can be expensive as it is still sold as a premium. USB 4 is about the speed of medium priced PCIe 4 NVMe SSDs. If buying a new computer, you would look for USB 4 and buy a matching NVMe SSD in a USB 4 enclosure for frequent use or a quick backup when out on the road. Keep your SATA III disks for an extra set of backups when in your office.
More than 4 TB
8 TB NVMe SSDs are expensive and often double sided, creating cooling problems. 3.5 inch magnetic disks still have a price advantage and are available up past 20 TB, giving you the option of massive storage in a manageable set of disks.
My old desktop has an SSD boot disk and can fit a further 5 SATA III disks. If configured as RAID 5, that would be 4 data disks and one redundant disk. 4 * 6 Gbps is 24 Gbps or about 2.5 GBps, the speed of PCIe 3 SSDs or medium priced PCIe 4 SSDs. 4 * 20 TB is 80 TB in what looks like one big disk.
The same capacity in NVMe SSDs, in affordable NVMe SSDs, would currently be 25 * 4 TB. There are no adaptor cards for an array like that.
There are tower PCs with 11 disk slots and motherboards with 8 SATA connections plus a slot for an expansion board for another 4 SATA disks. 11 disks as RAID 5 with 10 data disks and one redundant. 10 * 20 TB is 200 TB. All affordable and practical compared to M.2 NVMe SSDs.
Summary
Some disks are worth reusing, In Australia, the cost of new hardware limits reuse to big CMR disks while any small disk or SMR disk is just junk. In other economies the reuse range is wider. Plan ahead to look at the best point to upgrade with minimum interruption to your activity.
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