4 ms·

Does anyone chain SATAs in their home PC builds? Like IDEs it's been sold as a feature to SATA since the inception, but I always assumed that it was like IDE:

Does anyone chain SATAs in their home PC builds? Like IDEs it's been sold as a feature to SATA since the inception, but I always assumed that it was like IDE: a part of the protocol no SATA chip provider bothered to debug, or even implement. I think there were raid/NAS boxes that actually did it...

gerdesj 5y ago
This is all from memory, so treat with caution. The S in SATA is serial. The older IDE jobs are PATA - parallel. Two PATA drive share the available bandwidth (for want of a better word) and multiple SATAs have all the bandwidth available simultaneously to each device. Copying from one PATA disk to another on the same bus is horrible - in out, in out shake it all about at a few 10s of MBs-1. Copying from one SATA to another runs at full speed. For real speed you need SSD and hardware RAID with whopping caches and a price to match. For huge storage, reliability and a fairly eye watering price, why not use SSD to cache fast SAS 2.5" spinning rust with a decent hardware RAID. Oh I've just started to specify a SAN/NAS!
- bombcar 5y ago
  SAS allows "breakouts" and I think they may have updated SATA to allow something similar.
  - kevin_thibedeau 5y ago
    SATA has always supported port multipliers. Backblaze used them in the early days for their storage pods.
    - gerdesj 5y ago
      OK, so you kids know what you are on about. Am I roughly correct in my summation?
duskwuff 5y ago
I think you might be confusing chaining with some other feature. SATA has always been a point-to-point link, not a multidrop bus. SATA port multipliers are a thing, but they're active devices with multiple SATA transceivers, not a passive splitter. Support for port multipliers exists in most operating systems.
rodgerd 5y ago
Port multipliers exist, and do work, but they are incredibly finicky. The precise set of combinations of HBA, multiplier, kernel driver, and drives can be a nightmare - once USB 3 became available and reliable I largely lost interest.

gerdesj 5y ago

This is all from memory, so treat with caution. The S in SATA is serial. The older IDE jobs are PATA - parallel. Two PATA drive share the available bandwidth (for want of a better word) and multiple SATAs have all the bandwidth available simultaneously to each device. Copying from one PATA disk to another on the same bus is horrible - in out, in out shake it all about at a few 10s of MBs-1. Copying from one SATA to another runs at full speed. For real speed you need SSD and hardware RAID with whopping caches and a price to match. For huge storage, reliability and a fairly eye watering price, why not use SSD to cache fast SAS 2.5" spinning rust with a decent hardware RAID. Oh I've just started to specify a SAN/NAS!

bombcar 5y ago
SAS allows "breakouts" and I think they may have updated SATA to allow something similar.
- kevin_thibedeau 5y ago
  SATA has always supported port multipliers. Backblaze used them in the early days for their storage pods.
  - gerdesj 5y ago
    OK, so you kids know what you are on about. Am I roughly correct in my summation?

duskwuff 5y ago

I think you might be confusing chaining with some other feature. SATA has always been a point-to-point link, not a multidrop bus. SATA port multipliers are a thing, but they're active devices with multiple SATA transceivers, not a passive splitter. Support for port multipliers exists in most operating systems.

rodgerd 5y ago

Port multipliers exist, and do work, but they are incredibly finicky. The precise set of combinations of HBA, multiplier, kernel driver, and drives can be a nightmare - once USB 3 became available and reliable I largely lost interest.