{"id":6401,"date":"2021-03-05T20:19:20","date_gmt":"2021-03-05T18:19:20","guid":{"rendered":"https:\/\/tekmart.co.za\/t-blog\/?p=6401"},"modified":"2021-03-05T20:19:21","modified_gmt":"2021-03-05T18:19:21","slug":"ssd-raid-101-the-essentials-of-flash-storage-and-raid","status":"publish","type":"post","link":"https:\/\/tekmart.co.za\/t-blog\/ssd-raid-101-the-essentials-of-flash-storage-and-raid\/","title":{"rendered":"SSD Raid 101: The essentials of flash storage and Raid"},"content":{"rendered":"Reading Time-approximately:<\/span> 4<\/span> minutes<\/span><\/span>\n

Flash storage is mainstream, but what do storage professionals need to know about Raid when used with SSDs? We look at Raid fundamentals, and supplier implementations.<\/strong><\/h2>\n\n\n\n
\"Antony<\/figure>\n\n\n\n

By Antony Adshead<\/a><\/p>\n\n\n\n

A fundamental keystone of data protection,\u00a0Raid (redundant array of independent disks)\u00a0has been around for decades.<\/p>\n\n\n\n

The building blocks are very simple. Multiple disk drives allow data to be distributed via striping and\u00a0mirroring, or sets of\u00a0parity\u00a0data allow a failing unit to be rebuilt by reference to data on healthy media.<\/p><\/blockquote><\/figure>\n\n\n\n

But what has been the impact of solid-state media on the use of Raid?<\/p>\n\n\n\n

We\u2019ll look in detail at the Raid options available from the main flash array makers below.<\/p>\n\n\n\n

Broadly speaking, however, when an all-flash array is a legacy product that\u2019s been retrofitted with flash capacity then you find Raid levels that span the possible combinations of mirroring, striping and parity are available (ie, 1, 10, 5, 6), as they would have been in the HDD-equipped product.<\/p><\/blockquote>\n\n\n\n

Meanwhile, options are more limited on many of the newer startups\u2019 all-flash arrays and some of the big six suppliers\u2019 newer arrays, and seem to major on parity-based Raid levels (5 and 6) \u2013 sometimes their own flavour with branding to suit \u2013 and even in the case of NetApp, its own triple parity Raid.<\/p>\n\n\n\n

But\u00a0that\u2019s a broad sweep. Let\u2019s recap on\u00a0the basics of Raid.\u00a0<\/p>\n\n\n\n

Raid fundamentals<\/strong><\/h3>\n\n\n\n

While Raid is implemented in many variants, it is all built on combinations of possible characteristics based around striping (which aids speed of access more than data protection), mirroring and parity.<\/p>\n\n\n\n

So, for example,\u00a0Raid 1\u00a0mirrors data between disks while\u00a0Raid 10\u00a0stripes data across mirrored pairs, and these provide good read and write performance.<\/p>\n\n\n\n

Meanwhile Raid 5 is based on parity for data protection\/rebuilds and maximises capacity, but delivers less well on write\u00a0input\/output (I\/O). Raid 6 boosts data protection over Raid 5, due to the extra parity data it stores.<\/p><\/blockquote>\n\n\n\n

Stripe\u00a0set size is the number of disks that data is written to. With a bigger stripe set size, data is written to more drives and you\u2019ll get better I\/O performance.<\/p>\n\n\n\n

Be aware, however, that large stripe sets can result in disk rebuild issues due to unrecoverable read errors.<\/p>\n\n\n\n

And, of course,\u00a0Raid rebuild\u00a0times increase significantly as drive capacities grow.<\/p>\n\n\n\n

Raid has continued to evolve and we have seen new protection methods that use the essential components of Raid, but that distribute data and parity information in new ways.<\/p>\n\n\n\n

So is Raid relevant to the world of flash drives?<\/em><\/strong><\/p>\n\n\n\n

Well, yes. Despite their differences with spinning disk HDDs, flash drives do fail.<\/p>\n\n\n\n

There is always a risk of component failure and eventually a flash drive will fail because they have limited write I\/O capacity.<\/p>\n\n\n\n

This means some protection is required to cater for failure scenarios, and\u00a0suppliers that sell flash have implemented Raid in ways that vary from the standard levels to their own proprietary formats.<\/p><\/blockquote>\n\n\n\n

Raid in flash array products<\/strong><\/h3>\n\n\n\n

Dell EMC<\/strong> offers all-flash and hybrid flash VMAX, Unity and SC series arrays. These all use standard Raid levels, with 5 and 6 in VMAX in configurations that include 7+1 parity disk, as well as 3+1, 6+2 and 14+2. Unity and SC series arrays offer Raid 5 and 6 plus Raid 10, or Raid 1\/0 as Dell EMC calls it. The all-flash-only XtremIO uses its own XDP, which stands for Xtremio Data Protection, a so-called\u00a0\u201cmodified diagonal parity Raid-6 variant\u201d.<\/p>\n\n\n\n

Fujitsu\u2019s<\/strong> block-access Eternus all-flash arrays come as the small and medium sized enterprise-targeted AF250S2 that scales to 737TB and the enterprise-class AF650S2 that goes to nearly 3PB. Raid levels available are 0, 1, 10, 5 and the parity\/striping\u00a0Raid 50.<\/p>\n\n\n\n

Hewlett Packard Enterprise\u2019s (HPE)<\/strong> high-end 3PAR StoreServ SAN platforms come in three models that scale up to several petabytes in capacity. They can all be configured as all-flash or hybrid (as well as all-HDD) and offer Raid 1, Raid 5 and Raid 6 data protection. Early\u00a0in 2017, HPE\u00a0acquired all-flash startup Nimble Storage. Those arrays come in three sizes that range from a few TB of capacity to several hundred and have Nimble\u2019s triple-parity Raid with claimed\u00a0six nines\u00a0availability.<\/p>\n\n\n\n

Hitachi Vantara\u2019s<\/strong> F-series all-flash arrays in its virtual storage product line come in four models that go up to capacities of around 2,300 drives. They support Raid 10, Raid 5 and Raid 6.<\/p>\n\n\n\n

NetApp<\/strong> \u2013 NetApp\u2019s all-flash AAF (All-Flash FAS) arrays provide for Raid DP (its implementation of Raid 6) or Raid TEC, which stands for Triple Erasure Coding. This is a feature of NetApp\u2019s\u00a0Data ONTAP 9\u00a0operating environment that provides for a third parity disk to ensure the safety and speed of disk rebuilds. Meanwhile, NetApp\u2019s\u00a0SolidFire\u00a0arrays use their own Helix \u201cRaid-less\u201d data protection in which two copies of data are distributed through nodes in the cluster. Finally, NetApp\u2019s EF series flash arrays use Raid levels 0, 1, 5, 6 and 10. E-Series arrays date back to NetApp\u2019s\u00a0acquisition of Engenio in 2011, whose arrays were designed for spinning disk.<\/p>\n\n\n\n

IBM<\/strong> offers the all-flash FlashSystem and Storwize all-flash arrays, as well as the DS8880F products. The FlashSystem V900 offers between a few tens of TB and nearly 2PB with Raid 5. The FlashSystem 900 comes with\u00a03D TLC NAND\u00a0and Raid 5.<\/p>\n\n\n\n

IBM adds so-called \u201cvariable stripe Raid\u201d, which provides for bad data planes in the NAND chip to have their data shipped to healthy ones. Adding this feature to system-level Raid 5 is called Two Dimensional Raid by IBM.<\/p>\n\n\n\n

IBM\u2019s StorWize<\/strong> F-suffixed all-flash arrays come with Raid levels 0, 1, 5, 6 and 10. The V7000F supports 760 drives of up to 15TB (3,040 in a cluster) while the V5030F supports up to 1,520 in a cluster.<\/p>\n\n\n\n

The DS8880F series all-flash arrays come with Raid levels 5, 6 and 10 with capacities that go over 1PB.<\/p><\/blockquote>\n\n\n\n

Kaminario offers the K2 all-flash array, which comes in capacity units of K-blocks that can take it up to around 4PB.\u00a0Kaminario\u00a0also favours dual parity in its K-Raid scheme.<\/p>\n\n\n\n

Pure Storage\u2019s FlashArray\/\/M arrays come in a number of sizes from a few tens of TB to over 1PB. Raid HA is\u00a0Pure\u2019s\u00a0take on things and is a dual-parity Raid scheme, so like Raid 6.<\/p>\n\n\n\n

Western Digital-owned\u00a0Tegile\u2019s IntelliFlash arrays offer block and file access in nodes that range from a few hundred TB to nearly 2PB. The company\u2019s datasheets aren\u2019t too forthcoming but speak of \u201cmultiple Raid\/mirroring options\u201d that include dual-parity and two- and three-way mirroring.<\/p>\n\n\n\n

Tintri\u2019s key all-flash offerings are the EC series that range from tens of TB to tens of PB. Its T1000 offers all-flash for remote office\/branch office locations. Dual parity Raid 6 is the only option in\u00a0Tintri.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"

Reading Time-approximately:<\/span> 4<\/span> minutes<\/span><\/span>Flash storage is mainstream, but what do storage professionals need to know about Raid when used with SSDs? We look at Raid fundamentals, and supplier implementations. By Antony Adshead A fundamental keystone of data protection,\u00a0Raid (redundant array of independent disks)\u00a0has been around for decades. The building blocks are very simple. Multiple disk drives allow data to be distributed via striping<\/p>\n

Read More<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[221,4,30,3],"tags":[],"class_list":["post-6401","post","type-post","status-publish","format-standard","hentry","category-computer-storage-hardware","category-datacenter-news","category-expert-advise-and-opinion","category-industry-news-and-expert-advise"],"_links":{"self":[{"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/posts\/6401","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/comments?post=6401"}],"version-history":[{"count":1,"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/posts\/6401\/revisions"}],"predecessor-version":[{"id":6402,"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/posts\/6401\/revisions\/6402"}],"wp:attachment":[{"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/media?parent=6401"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/categories?post=6401"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tekmart.co.za\/t-blog\/wp-json\/wp\/v2\/tags?post=6401"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}