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The oft repeated performance reason is that hardware RAID controllers have battery backed write cache, which really improves durable write performance; somethin

by spudlyo 10y ago

The oft repeated performance reason is that hardware RAID controllers have battery backed write cache, which really improves durable write performance; something traditional relational DBs do quite a lot of. Also, these machines were built by DB people, who have traditionally placed a lot of value in hardware RAID controllers, and to be fair, the HP controllers worked well with HDDs. Also ZFS wasn't a realistic option for production Linux in 2013. Me personally, I'm not a fan of exotic proprietary hardware, I much prefer working with JBOD disk setups and software RAID where appropriate.

creshal 10y ago
> The oft repeated performance reason is that hardware RAID controllers have battery backed write cache, which really improves durable write performance; something traditional relational DBs do quite a lot of. Don't all enterprise SSDs come with their own backup capacitors?
- baruch 10y ago
  They do. You get an ack for a write before it reaches the media as long as the supercaps are deemed ok.
- virtualwhys 10y ago
  > Don't all enterprise SSDs come with their own backup capacitors? Yes, but the cost of such drives makes rolling the dice with consumer grade drives appealing to some[1]. From the same thread, here's a word of warning from a Stackoverflow devops engineer[2] wrt to lack of capicitors on consumer grade drives and the perfect storm that can occur when UPS goes down in a power failure (unlike with spinning disks hardware RAID is unable prevent data corruption/loss in this case). [1] https://laur.ie/blog/2015/06/ssds-a-gift-and-a-curse/ https://laur.ie/blog/2015/06/ssds-a-gift-and-a-curse/ [2] https://laur.ie/blog/2015/06/ssds-a-gift-and-a-curse/#comment-121887 https://laur.ie/blog/2015/06/ssds-a-gift-and-a-curse/#commen...
  - kpil 10y ago
    I think my consumer-grade Intel S3500 SSD have some kind of power-loss protection. I don't think that professional devices are 100% fail-proof either. I vaguely remember some test where they setup a test with forced power failures during heavy writes, and they zapped all drives but a few eventually. Something that worried me was that the failure mode quite often seemed to be a totally bricked SSD.
    - creshal 10y ago
      > I think my consumer-grade Intel S3500 SSD have some kind of power-loss protection. The fine-print is important here. Crucial (IIRC) advertises some of its low-end consumer series with power-loss protection… against internal data corruption of the Flash Translation Layer. AKA "We won't completely brick the entire device if you pull power!" Err… thank you? Why are you advertising this as feature?
      - imtringued 10y ago
        Because OCZ SSDs used to have a failure rate of more than 50% caused by powerloss.
        Something1234 10y ago
        Really,if this is true I don't think I will buy another OCZ SSD. Which brand is the best for reliability right now?
        creshal 10y ago
        OCZ already went bankrupt over that scandal and was bought up… in 2013.
- dmm 10y ago
  Are you saying that most SSDs lose data they claimed was saved to stable storage in the event of power loss? That's crazy. Filesystems are greatly complicated by the need to be resistant to power loss. What is the point of all that complication if the block device is just going to throw away those guarantees? If we're giving up on power loss safety I can make a super fast filesystem by making fsync a no-op and keeping everything in ram until I feel like writing it.
  - creshal 10y ago
    > Are you saying that most SSDs lose data they claimed was saved to stable storage in the event of power loss? Same with HDDs. That's why battery-backed hardware RAIDs (+ disabling this cache on the connected disks) are a thing in the first place. > What is the point of all that complication if the block device is just going to throw away those guarantees? Ask that storage manufacturers.

by spudlyo 10y ago

creshal 10y ago

> The oft repeated performance reason is that hardware RAID controllers have battery backed write cache, which really improves durable write performance; something traditional relational DBs do quite a lot of. Don't all enterprise SSDs come with their own backup capacitors?

baruch 10y ago
They do. You get an ack for a write before it reaches the media as long as the supercaps are deemed ok.
virtualwhys 10y ago
> Don't all enterprise SSDs come with their own backup capacitors? Yes, but the cost of such drives makes rolling the dice with consumer grade drives appealing to some[1]. From the same thread, here's a word of warning from a Stackoverflow devops engineer[2] wrt to lack of capicitors on consumer grade drives and the perfect storm that can occur when UPS goes down in a power failure (unlike with spinning disks hardware RAID is unable prevent data corruption/loss in this case). [1] https://laur.ie/blog/2015/06/ssds-a-gift-and-a-curse/ https://laur.ie/blog/2015/06/ssds-a-gift-and-a-curse/ [2] https://laur.ie/blog/2015/06/ssds-a-gift-and-a-curse/#comment-121887 https://laur.ie/blog/2015/06/ssds-a-gift-and-a-curse/#commen...
- kpil 10y ago
  I think my consumer-grade Intel S3500 SSD have some kind of power-loss protection. I don't think that professional devices are 100% fail-proof either. I vaguely remember some test where they setup a test with forced power failures during heavy writes, and they zapped all drives but a few eventually. Something that worried me was that the failure mode quite often seemed to be a totally bricked SSD.
  - creshal 10y ago
    > I think my consumer-grade Intel S3500 SSD have some kind of power-loss protection. The fine-print is important here. Crucial (IIRC) advertises some of its low-end consumer series with power-loss protection… against internal data corruption of the Flash Translation Layer. AKA "We won't completely brick the entire device if you pull power!" Err… thank you? Why are you advertising this as feature?
    - imtringued 10y ago
      Because OCZ SSDs used to have a failure rate of more than 50% caused by powerloss.
      - Something1234 10y ago
        Really,if this is true I don't think I will buy another OCZ SSD. Which brand is the best for reliability right now?
        creshal 10y ago
        OCZ already went bankrupt over that scandal and was bought up… in 2013.
dmm 10y ago
Are you saying that most SSDs lose data they claimed was saved to stable storage in the event of power loss? That's crazy. Filesystems are greatly complicated by the need to be resistant to power loss. What is the point of all that complication if the block device is just going to throw away those guarantees? If we're giving up on power loss safety I can make a super fast filesystem by making fsync a no-op and keeping everything in ram until I feel like writing it.
- creshal 10y ago
  > Are you saying that most SSDs lose data they claimed was saved to stable storage in the event of power loss? Same with HDDs. That's why battery-backed hardware RAIDs (+ disabling this cache on the connected disks) are a thing in the first place. > What is the point of all that complication if the block device is just going to throw away those guarantees? Ask that storage manufacturers.