5 ms·

> So if you pay for 1GB of storage, they probably actually store 5GB of data or more for you The actual factor is most likely around 1.4-1.5x and for sure can’

> So if you pay for 1GB of storage, they probably actually store 5GB of data or more for you The actual factor is most likely around 1.4-1.5x and for sure can’t be any more than 2.2x in this day and age. Dumbest possible implementation will be “only” 3x so no it’s nowhere close to 5gb Edit: looks like it’s public so i can actually tell you that google uses RS 3,2 which gives 1.5 replication factor. When i was there a few years ago storage folks told me they never lost a single stripe of data

pests 3y ago
A common problem would be throughput though. Storage capacity scales much faster than access speed. If you are storing an item only 3 times and lets say each storage location gives you 50,000 IOPS max then you can only ever service 150,000 IOPS of this item which might not be enough.
- dilyevsky 3y ago
  Vast majority of data rarely (if ever) gets read so you use a cache for that
teraflop 3y ago
Presumably Google also keeps backups, though, right?
- dilyevsky 3y ago
  Yes they also store to tape
  - AuthorizedCust 3y ago
    That means 2X at a minimum. Then RAID overhead. Possibly other hot or warm copies ready to take over instantly.
    - dilyevsky 3y ago
      And tape costs same as ssd/spindles in your calculations?
- dietr1ch 3y ago
  And mirrors to at least one extra datacenter as they can lose bandwidth with a fiber getting cut, become unreachable due to networking snafu, or even burn down entirely.
pclmulqdq 3y ago
Those numbers are for Colossus. Blobstore, which backs the cloud object store, is different, and used to be a lot higher.
- dilyevsky 3y ago
  Yeah those aren’t public afaik, iirc they adjusted replication for cold data
killingtime74 3y ago
What does RS 3,2 stand for? Thanks
- dilyevsky 3y ago
  Reed-Solomon erasure coding. 2 data blocks, one parity. Basically raid-6 but distributed
- deleted 3y ago
  [deleted]
londons_explore 3y ago
But thats within one cell... But data will be stored in more than one cell to deal with scheduled and unscheduled downtime of the cell...
- dilyevsky 3y ago
  You have pay more for that
  - deleted 3y ago
    [deleted]
  - smueller1234 3y ago
    Not with GCS, you don't. https://cloud.google.com/storage/docs/availability-durability https://cloud.google.com/storage/docs/availability-durabilit... Are you thinking of Persistent Disk (PD) and Replicated PD? (I work on storage at Google.)
    - dilyevsky 3y ago
      I was thinking of gcp regions in which case you do have to pay for it. For colossus cells within a single regions you obviously don't but I don't know enough how it maps it out down there and whether it just moves data around in the event of PCR

pests 3y ago

A common problem would be throughput though. Storage capacity scales much faster than access speed. If you are storing an item only 3 times and lets say each storage location gives you 50,000 IOPS max then you can only ever service 150,000 IOPS of this item which might not be enough.

dilyevsky 3y ago
Vast majority of data rarely (if ever) gets read so you use a cache for that

teraflop 3y ago

Presumably Google also keeps backups, though, right?

dilyevsky 3y ago
Yes they also store to tape
- AuthorizedCust 3y ago
  That means 2X at a minimum. Then RAID overhead. Possibly other hot or warm copies ready to take over instantly.
  - dilyevsky 3y ago
    And tape costs same as ssd/spindles in your calculations?
dietr1ch 3y ago
And mirrors to at least one extra datacenter as they can lose bandwidth with a fiber getting cut, become unreachable due to networking snafu, or even burn down entirely.

pclmulqdq 3y ago

Those numbers are for Colossus. Blobstore, which backs the cloud object store, is different, and used to be a lot higher.

dilyevsky 3y ago
Yeah those aren’t public afaik, iirc they adjusted replication for cold data

killingtime74 3y ago

What does RS 3,2 stand for? Thanks

dilyevsky 3y ago
Reed-Solomon erasure coding. 2 data blocks, one parity. Basically raid-6 but distributed
deleted 3y ago
[deleted]

londons_explore 3y ago

But thats within one cell... But data will be stored in more than one cell to deal with scheduled and unscheduled downtime of the cell...

dilyevsky 3y ago
You have pay more for that
- deleted 3y ago
  [deleted]
- smueller1234 3y ago
  Not with GCS, you don't. https://cloud.google.com/storage/docs/availability-durability https://cloud.google.com/storage/docs/availability-durabilit... Are you thinking of Persistent Disk (PD) and Replicated PD? (I work on storage at Google.)
  - dilyevsky 3y ago
    I was thinking of gcp regions in which case you do have to pay for it. For colossus cells within a single regions you obviously don't but I don't know enough how it maps it out down there and whether it just moves data around in the event of PCR