AS SSD Benchmark vs ATTO Disk Benchmark: Two Different Views of Drive Speed
ATTO Disk Benchmark and AS SSD Benchmark are two of the oldest names in storage testing, but they look at a drive from opposite ends. ATTO sweeps sequential transfers across many block sizes and shows you a curve. AS SSD Benchmark concentrates on a small set of defined tests — sequential, 4K, 4K with 64 threads and access time — and rolls them into a total score. This page explains when each view is the useful one. You can download AS SSD Benchmark from this site; ATTO itself is distributed by its vendor, as explained below.
What ATTO does differently
ATTO Disk Benchmark comes from ATTO Technology, a company that builds storage connectivity products, and it is distributed as vendor freeware — the official download asks you to fill in a form, which is why many people first meet it through download mirrors instead. Its signature test measures sequential read and write throughput across a ladder of transfer sizes, from 512 bytes up to 64 MB. The resulting graph shows the point at which a drive reaches its full sequential speed: tiny transfers are slow on almost everything, throughput climbs as the transfer size grows, and then it levels off. That curve is exactly what a manufacturer or system builder wants when checking that a drive, controller and connection are performing as a combination.
Because the emphasis is sequential, ATTO is generous to drives. A modern SSD will usually show its most flattering numbers here, close to the headline speeds printed on the box, because retail packaging figures are also sequential. That does not make ATTO wrong — large file transfers, video capture and media work really are sequential workloads. It does mean an ATTO graph alone cannot tell you how a drive behaves as an operating-system drive, where small random reads and writes dominate.
What AS SSD Benchmark does differently
AS SSD Benchmark was written specifically for solid-state drives. Its synthetic tests do not use the operating system cache, and alongside its sequential row it measures random 4K performance twice: once in the ordinary single-threaded pattern and once spread across 64 threads, which exposes how a drive and its controller handle queued commands. It also records access time, and its simplified score — Read = Seq × 0.1 + 4K + 4K-64Thrd, and the same for Write — deliberately weights the random results far more heavily than the sequential one. A drive can therefore look ordinary in AS SSD while looking spectacular in ATTO, and for a Windows system drive the AS SSD view is usually the more honest predictor of how responsive the machine will feel.
AS SSD adds two practical extras. The Copy-Benchmark times ISO, Program and Game copy scenarios using the operating system’s own copy functions, and the Compression-Benchmark charts performance against data compressibility. The main window also shows the controller driver and partition alignment status, so a single run can reveal a misconfigured system, not just a slow drive. None of that appears in an ATTO graph.
Side-by-side comparison
| Dimension | AS SSD Benchmark | ATTO Disk Benchmark |
|---|---|---|
| What it measures | Seq, 4K, 4K-64Thrd and access time, plus Copy and Compression tests | Sequential read and write across transfer sizes from 512 B to 64 MB |
| Score / result form | Per-test MB/s or IOPS plus Read, Write and Total scores | Throughput curve by transfer size; no total score |
| Platform | Windows only; portable | Windows (vendor distribution) |
| Licence and price | Freeware by Alexej Schepeljanski; free | Vendor freeware from ATTO Technology; free, official download requires completing a form |
| Maintenance status | Final version 2.0.7316.34247, January 2020 | Long-running vendor tool; widely mirrored versions date from the late 2010s onward |
| Best for | Judging a drive as a system disk: random performance, total score, copy behaviour, alignment | Checking peak sequential throughput and how throughput scales with transfer size; vendor and builder validation |
Reading the two results together
A healthy drive tells a consistent story in both tools: ATTO’s curve climbs quickly and flattens near the drive’s sequential ceiling, while AS SSD’s sequential row lands in a similar range and its 4K rows show the random performance underneath. Warning signs are mismatches. If ATTO reaches full speed only at very large transfer sizes, small-file work will suffer. If AS SSD’s 4K write is far below what comparable drives achieve while sequential results are normal, look at alignment, controller mode and free space before blaming the hardware — AS SSD’s own header display is designed to surface exactly those configuration problems.
For a broader view of how the major tools divide the work, see our roundup of the best SSD benchmark tools and the head-to-head AS SSD Benchmark vs CrystalDiskMark, which covers the other tool most people pair with ATTO.
Common mistakes when comparing the two
The most frequent error is quoting ATTO’s peak sequential figure as if it were the drive’s everyday speed. That number is real, but it describes large, queued sequential transfers — the easiest work a drive ever does. Everyday Windows use is dominated by small reads and writes scattered across the disk, which is why AS SSD weights its 4K results so heavily in its score. A second mistake is comparing results gathered at different queue settings or test lengths and treating a small difference as meaningful; run both tools back to back on an idle system, with the drive in the same state, before drawing any conclusion. A third mistake is ignoring the system around the drive: the same SSD will post different numbers behind a slower controller, in a thermally cramped enclosure, or on a nearly full volume, in both tools. Benchmarks measure a drive in a system, never a drive in the abstract, and both ATTO and AS SSD are honest only when you keep that context attached to their results.
Verdict by scenario
Verifying a drive reaches its advertised sequential speed: ATTO. Choosing or troubleshooting a Windows system drive: AS SSD Benchmark, because 4K and 64-thread behaviour decide how the machine feels. Validating a build or a storage product: ATTO’s transfer-size curve, ideally with AS SSD as a second opinion. Used together they take minutes and describe both the ceiling and the foundations of a drive’s performance.
Start with the official AS SSD file on our download page — it is a small portable program, so you can run it alongside ATTO without installing anything.