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Difference between revisions of "Hardware"
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Add section for Optane / 3D XPoint SSDs
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The ATA TRIM command in SATA 3.0 and earlier is a non-queued command. Issuing a TRIM command on a SATA drive conforming to SATA 3.0 or earlier will cause the drive to drain its IO queue and stop servicing requests until it finishes, which hurts performance. SATA 3.1 removed this limitation, but very few SATA drives on the market are conformant to SATA 3.1 and it is difficult to distinguish them from SATA 3.0 drives. At the same time, SCSI UNMAP has no such problems. | The ATA TRIM command in SATA 3.0 and earlier is a non-queued command. Issuing a TRIM command on a SATA drive conforming to SATA 3.0 or earlier will cause the drive to drain its IO queue and stop servicing requests until it finishes, which hurts performance. SATA 3.1 removed this limitation, but very few SATA drives on the market are conformant to SATA 3.1 and it is difficult to distinguish them from SATA 3.0 drives. At the same time, SCSI UNMAP has no such problems. | ||
= Optane / 3D XPoint SSDs = | |||
These are SSDs with far better latencies and write endurance than NAND flash SSDs. They are byte addressable, such that ashift=9 is fine for use on them. Unlike NAND flash SSDs, they do not require any special power failure protection circuitry for reliability. However, they cost more per GB than NAND flash (as of 2020). They make excellent SLOG devices. | |||
= Power = | = Power = | ||