Storage

HDD vs SSD vs Flash

Placing Oracle redo logs on SSD is not recommended. Exadata now has a “Smart Flash Logging” feature that uses redo logs on SSD. Note that it uses redo logs *also* on SSD. This feature allows Oracle to write redo in parallel to a file on SSD and a file on the magnetic disk, and finish the operation when one of the calls is successful. This is a no-lose situation that can only improve performance. This is not the case if you place your redo logs on both SSD and magnetic disks yourself, in which case the redo write will finish when the slowest device finishes writing, making it a no-win situation.

Even if you place all copies of your redo logs on the SSD, you are still likely to see performance degradation. This is expected because as we discussed before, SSD doesn’t have any performance benefit for sequential writes of the type redo logs usually experience, and it may even end up being slower. Our experience at Pythian with customers attempting to place redo logs on SSD confirms this issue, and so do the tests ran by Guy Harrison.


https://blog.pythian.com/de-confusing-ssd-for-oracle-databases/


SSD is not the same as an all-flash array. An all-flash array is able to avoid the consequences of [the above] restrictions by managing the flash globally, so that erases do not block reads and writes.


https://flashdba.com/2013/08/22/storage-myths-put-oracle-redo-on-ssd/


SSD is not for long-term storage.https://www.quora.com/Why-is-SSD-not-a-good-option-for-long-term-storagehttps://www.quora.com/What-is-the-best-storage-for-a-long-term-data-store-HDD-or-SSDhttps://www.quora.com/Is-the-modern-new-2023-built-SSD-reliable-for-long-term-storage

SAN vs NAS

NAS better for sharing files, SAN usually better for databases

CMR vs SMR

SMR is not recommended for...

Identifying CMR/SMR

this is usually found on SSDs, there is no benefit of this on CMR drives so they are unlikely to include support
  • For Windows you can identify TRIM support using a tool like CrystalDiskMark.
  • For UNIX you can use a tool like GSmartControl.

Acronyms

Bibliography


https://blog.seagate.com/business/why-are-hard-drives-built-differently-and-does-it-matter/https://blog.seagate.com/business/video-choose-the-right-drive-for-the-right-workload/https://www.sqlservercentral.com/blogs/the-fundamentals-of-storage-systems-introductionhttps://www.sqlservercentral.com/blogs/fundamentals-of-storage-systems-the-basics-of-spinning-diskshttps://www.broadbandbuyer.com/#
RAIDhttp://www.raid-calculator.com/default.aspx
Filesystemshttps://www.iperiusbackup.net/en/refs-vs-ntfs-differences-and-performance-comparison-when-to-use/
Performancehttps://hdd.userbenchmark.com/https://superuser.com/questions/680589/how-can-i-achieve-maximum-sustained-sequential-disk-write-performancehttps://learn.microsoft.com/en-us/biztalk/technical-guides/using-the-performance-analysis-of-logs-pal-toolhttps://github.com/clinthuffman/PAL
IOPShttp://storagearchitect.blogspot.com/2008/09/how-many-iops.htmlhttps://en.wikipedia.org/wiki/IOPS#Exampleshttps://wiki.horde.org/HardwareRequirements
NAShttps://www.reddit.com/r/PleX/comments/11b7afx/what_would_be_the_best_nas_server_for_a_plex/https://www.androidcentral.com/best-nas-plexhttps://uk.pcmag.com/nas/14710/the-best-nas-network-attached-storage-devices
vSANhttps://blogs.vmware.com/virtualblocks/2019/04/18/vsan-disk-groups/
SSDhttps://ssd.userbenchmark.com/https://www.quora.com/What-is-the-average-read-write-speed-of-an-SSD-hard-drivehttps://www.quora.com/Why-is-SSD-not-a-good-option-for-long-term-storagehttps://www.quora.com/Is-the-modern-new-2023-built-SSD-reliable-for-long-term-storage
CMR/SMRhttps://www.broadbandbuyer.com/Advice/4348-cmr-vs-smr-what-the-difference/https://techwiser.com/smr-vs-cmr-drives-comparison/https://www.seagate.com/gb/en/internal-hard-drives/cmr-smr-list/https://blog.westerndigital.com/wd-red-nas-drives/https://toshiba.semicon-storage.com/ap-en/company/news/news-topics/2020/04/storage-20200428-1.html

Back in my first job, must have been about 1988, we had one of these (see video, right), made by Honeywell. It used one of those big blue 30 amp plugs but we didn't have enough 30 amp sockets, so we swapped it for a standard 13 amp 3 pin plug. Armed with some spare fuses, one of my jobs was to spin the disk up to a reasonable speed using my hand then slam the lid shut and shout, "Now!", to a colleague who would throw the switch on the socket.