There are many different issues that need to be taken into consideration when evaluating data storage options for post-production.\u00c2\u00a0 Cost is a primary factor to consider, since without that issue, there would be\u00c2\u00a0little to weight against high end systems.\u00c2\u00a0 Performance is key as well, for efficiency as well as creativity.\u00c2\u00a0 Reliability is a frequently undervalued consideration, that effects everything from insurance prices to stress levels.\u00c2\u00a0 The ability to share data effectively can be an important consideration, since post-production is usually a collabrative effort.<\/p>\n
The industry has responded with many different solutions, that vary in concept beyond recognition and in\u00c2\u00a0price by many orders of magnitude.\u00c2\u00a0 The earliest solutions involved video tape, analog replaced by digital recording.\u00c2\u00a0 Hard disks were introduced for random access to data, and now those are slowly beginning to be replaced by solid state flash chips.\u00c2\u00a0 Since this site is targeted to PC users, we will focus on hard disk based solutions, and the interfaces with which they can be accessed by a media workstation.<\/p>\n
Hard disks are produced with five popular interfaces:\u00c2\u00a0 IDE\/ATAPI, Serial-ATA (SATA), Small Computer System Interface (SCSI), Serial Attached SCSI (SAS), and Fibre Channel (FC).\u00c2\u00a0 IDE and SCSI interfaces are currently being phased out and replaced by their more capable and flexible\u00c2\u00a0Serial varients.\u00c2\u00a0 I know little of true Fibre Channel hard disks, but that format is rarely used in this industry.\u00c2\u00a0 That leaves only two options, which are now somewhat similar and compatible, SATA and SAS.\u00c2\u00a0 With identical connection cables, and both offered in 3.5″ and 2.5″ form factors, it is hard to tell the two options apart visually.\u00c2\u00a0 Their interfaces both support 300MB\/s, dedicated buses for each drive, and port splitting when that is not required.
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\nThe biggest differences between SATA and SAS are performance and\u00c2\u00a0cost, which eventually distill down to one issue:\u00c2\u00a0size.\u00c2\u00a0 SAS disks have slightly more capable and efficient\u00c2\u00a0electronics, run fewer platter, with less data, and much higher RPMs and faster I\/O and transfer rates.\u00c2\u00a0 SATA drives usually have much more storage capacity, lower speeds, and are always much cheaper.\u00c2\u00a0 At first glance, high end post production work would seem suited for SAS drives, since moving picture\u00c2\u00a0footage requires a higher data\u00c2\u00a0transfer rate than almost any other application of computing technology.<\/p>\n
There are four other factors, which when combined, weight much more heavily in favor of SATA.\u00c2\u00a0\u00c2\u00a0The first is price.\u00c2\u00a0 Since the\u00c2\u00a0difference in price per Gigabyte is currently so great, and SATA drives are not that different in their design or performance, a few quick calculations will reveal that while SAS disks have higher performance per drive, SATA disks deliver more performance per dollar, regardless of their storage capacity.\u00c2\u00a0\u00c2\u00a0Second is that the\u00c2\u00a0infrastructure needed to aggregate the performance of multiple disks (Raid arrays)\u00c2\u00a0will be\u00c2\u00a0required, regardless of which disk solution we choose.\u00c2\u00a0 This is\u00c2\u00a0due to the fact that\u00c2\u00a0HD resolutions and larger require much higher data transfer rates than any single drive can provide (unless compressed, and even then, fast disk access is beneficial).\u00c2\u00a0 The marginal cost to increase the number of drives being aggregated will be low in many cases.\u00c2\u00a0 The third factor is that digitalized\u00c2\u00a0footage requires a tremendous amount of storage space, once again contributing to the need for many hard drives to be combined.\u00c2\u00a0 Lastly, most of the popular solutions to improve reliability, do so by utilizing even more capacity, to store redundant information in the form of parity, or straight backups.<\/p>\n
These factors, when combined make a strong case for SATA disks, which have higher capacity at the expense of performance per drive.\u00c2\u00a0 If we are combining drives anyway, the performance benefits of SAS\u00c2\u00a0will usually be\u00c2\u00a0negated by combining more SATA drives for less money.\u00c2\u00a0 This is a case where quantity can clearly overcome quality in most instances.\u00c2\u00a0 As a side benefit, SATA drives usually have much greater capacities.<\/p>\n
The only time when SAS may be favorable, will be when there is little need for high capacity, and when there is value to smaller solutions.\u00c2\u00a0 Fewer SAS disks are required to reach a given level of performance, and will therefore be more portable, require less power, and frequently generate less heat and noise.\u00c2\u00a0 For visual effects, were a few seconds of footage are manipulated at very high quality, or short commercials, SAS may be a more efficient option.<\/p>\n
In most cases though, the numbers come down in favor of SATA by along shot.\u00c2\u00a0 Let’s imagine a two hour movie, with a 10:1 shooting ratio, giving us\u00c2\u00a020 hours of footage, and for the sake of example, let’s assume a data rate of 100MB\/s.\u00c2\u00a0 With 3600 seconds in an hour, that is 360000MB an hour, or 360GB.\u00c2\u00a0 20 hours of footage would require 7.2TB of storage.\u00c2\u00a0 Add 10% to avoid disk fragmentation, and you need an 8TB array.\u00c2\u00a0 With 1TB SATA disks you need 8, plus two more to support Raid 50.\u00c2\u00a0 You will have the bandwidth of eight drives, and assuming 50MB\/s each for SATA disks, and an efficient controller interface,\u00c2\u00a0that is 400 MB\/s, more than enough for our 100MB\/s files.\u00c2\u00a0 10 SATA drives at 1TB currently costs ago $3,000, and the Raid hardware will be required by both SATA and SAS, so it does not necessarily need to be factored in.\u00c2\u00a0 Now when onlining a production, not all footage is usually\u00c2\u00a0captured, but when you factor in captures, conformed exports, film and video colored versions, testless and texted masters, a 10:1 ratio will not be an inaccurate estimate.\u00c2\u00a0 Now I used round numbers, so that if the datarate of your format of choice is higher or lower, you can ajust accordingly. 200MB\/s footage would\u00c2\u00a0need 20 disks, but could get double performance.\u00c2\u00a0 50MB\/s footage would only need 5 disks, but could still expect 200MB\/s of performance.\u00c2\u00a0 Have less footage, I left a 4x overhead in this example with\u00c2\u00a020 hours of source, but I also used 1TB drives for my calculations.\u00c2\u00a0 With 10 hours, 500GB drives show SATA to be even more economically favorable.<\/p>\n
Now for a quick comparison to SAS, we start by noting that the maximum capacity is 300GB, and you can expect to pay at least $500 per disk.\u00c2\u00a0 Our 8TB example would require about thirty disks, assuming a Raid 50,\u00c2\u00a0striping together\u00c2\u00a0three Raid 5 arrays of ten disks. 27 data disks is 8.1TB for a cost of $15,000 in drives alone, not counting that it requires hardware for three 10 bay array enclosures instead of one.\u00c2\u00a0 From a performance perspective, assuming 80MB\/s per disk, you can get over 2GB\/s if you want to pay for an interface that fast, but remember that this is all for footage that is 100MB\/s.\u00c2\u00a0 2GB\/s might be good if you want to share it between multiple systems, but with that many users, usually multiple productions will be processed concurrently, requiring much more storage capacity anyway.\u00c2\u00a0 By multiplying up and down for different formats, it becomes clear that there is no way that SAS can economically catch up.<\/p>\n
So I hope this successfully establishes that SATA disk drives will almost always be the drive type of choice for post-production environments.\u00c2\u00a0 I plan to examine the different options for connecting these drive arrays\u00c2\u00a0to a workstation or group of systems in my next post.<\/p>\n","protected":false},"excerpt":{"rendered":"
There are many different issues that need to be taken into consideration when evaluating data storage options for post-production.\u00c2\u00a0 Cost is a primary factor to consider, since without that issue, there would be\u00c2\u00a0little to weight against high end systems.\u00c2\u00a0 Performance is key as well, for efficiency as well as creativity.\u00c2\u00a0 Reliability is a frequently undervalued […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[34,33,32],"_links":{"self":[{"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/posts\/13"}],"collection":[{"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/comments?post=13"}],"version-history":[{"count":0,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/posts\/13\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/media?parent=13"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/categories?post=13"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/tags?post=13"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}