Hybrid drives for servers
How to choose drives for the server? After all, it is necessary to take into account a number of factors, such as increased reliability, high speed of work, and also, which is especially important today - an affordable price. Classic hard drives are cheap, but even models with a spindle speed of 10 and 15 thousand revolutions per minituat often cannot provide an adequate level of performance. The ever-increasing density of consolidation of computing resources requires a corresponding increase in the performance of the disk subsystem, which only SSD-based solid-state drives can fully provide. Unfortunately, in spite of the annual growth of volumes and productivity of such drives, the relatively high price / volume ratio in many cases does not allow to completely switch to SSD.
An alternative to a full transition to SSD are still hybrid solutions using SSD as a cache or as a high-performance layer in more complex tier storage systems. At the same time, the use of even simple caching requires the installation of additional software products or the acquisition of equipment that supports the SSD cache. The task of simplifying the implementation of hybrid solutions can be solved by the use of hybrid disks (SSHD), which combine common mechanical HDD, flash memory and program caching layer in a common package. In fact, the integrated flash memory serves as a second-level cache for a hybrid disk, in which a much larger amount of data can fit in than a standard cache. Special algorithms analyze the frequency of access to certain data on the disk. The most requested data is copied to flash memory. The larger the amount of flash memory, the more data can be written to it for quick access to it.
Support for caching technology in operating systems has become an incentive for first SSDHD to spread on the market, although modern SSHD drives manage the caching process themselves. Since hybrid discs are available in standard form factors and are apparently indistinguishable from ordinary ones, they are increasingly being used in desktops and laptops, but they are not yet so common on servers.
Seagate can be called a pioneer in the creation of hybrid SSHD-drives. In 2007, 2.5-inch Seagate Momentus PSDs of 80, 120 and 160 gigabytes, designed for use in desktop systems, appeared. The first hybrid SSHD-models for servers appeared in 2013, they were custom-made for IBM and were intended for System X servers. Today, the company presents corporate customers with Seagate Enterprise Performance 10k HDD v8 and 15k HDD v5 hybrid discs with TurboBoost technology. Their feature is that, in addition to the usual 128 MB disk cache, the developers also integrated 32 gigabytes of eMLC NAND flash memory for read caching, as well as 8 megabytes of non-volatile NVRAM for write caching. Recall that eMLC memory has a several times higher resource in terms of the number of rewriting cycles compared to MLC memory, it is already actively used in SSD-drives for server use. TurboBoost technology can be compared with SSD caching in SAS RAID controllers, however, unlike the latter, it is completely independent from other components of the disk subsystem - the TurboBoost drive does not require the installation of additional software or the use of special equipment.
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As specific examples, consider two models - ST1800MM0088 and ST600MX0052. Both drives are made in the traditional form factor - a 2.5-inch case with a height of 15 mm, and support the SAS3 interface (12 Gbit / s). Model ST1800MM0088 is available with a volume of 1.8 terabytes, with 4 plates, 8 heads and a spindle speed of 10 thousand revolutions per minute. Model ST600MX0052 has a smaller volume - 600 gigabytes (3 plates, 6 heads) at a spindle speed of 15 thousand revolutions per minute. Both drives come with a cache of 128 megabytes, as well as 32 gigabytes of eMLC NAND memory. The manufacturer declared the following performance parameters: for ST600MX0052 - sequential access 180–246 Mb / s, with an average delay level of 2 milliseconds, and for ST1800MM0088 - sequential access 117–241 MB / s, with an average delay level of 2.9 milliseconds.
Seagate ST1800MM0088
Seagate ST600MX0052
Testing * showed the following features of these disks:
* Indicated performance gain for disk ST600MX0052 (600 GB, 15 thousand rpm) when filling the cache. Additional test parameters: block - 4096 bytes, queue depth - 32, FIO 2.1.14.
Drive Seagate ST600MX0052. Increased performance of random access by small blocks when filling the cache.
In general, Seagate Enterprise Performance hybrid drives with TurboBoost technology can be used in mission-critical server systems and storage systems as a replacement for conventional hard drives. With a suitable load (random access in small blocks, preferential read), they can provide significant performance gains without the need to implement separate SSD caching technologies.
The text was prepared based on materials from the True System company.
An alternative to a full transition to SSD are still hybrid solutions using SSD as a cache or as a high-performance layer in more complex tier storage systems. At the same time, the use of even simple caching requires the installation of additional software products or the acquisition of equipment that supports the SSD cache. The task of simplifying the implementation of hybrid solutions can be solved by the use of hybrid disks (SSHD), which combine common mechanical HDD, flash memory and program caching layer in a common package. In fact, the integrated flash memory serves as a second-level cache for a hybrid disk, in which a much larger amount of data can fit in than a standard cache. Special algorithms analyze the frequency of access to certain data on the disk. The most requested data is copied to flash memory. The larger the amount of flash memory, the more data can be written to it for quick access to it.
Support for caching technology in operating systems has become an incentive for first SSDHD to spread on the market, although modern SSHD drives manage the caching process themselves. Since hybrid discs are available in standard form factors and are apparently indistinguishable from ordinary ones, they are increasingly being used in desktops and laptops, but they are not yet so common on servers.
Seagate can be called a pioneer in the creation of hybrid SSHD-drives. In 2007, 2.5-inch Seagate Momentus PSDs of 80, 120 and 160 gigabytes, designed for use in desktop systems, appeared. The first hybrid SSHD-models for servers appeared in 2013, they were custom-made for IBM and were intended for System X servers. Today, the company presents corporate customers with Seagate Enterprise Performance 10k HDD v8 and 15k HDD v5 hybrid discs with TurboBoost technology. Their feature is that, in addition to the usual 128 MB disk cache, the developers also integrated 32 gigabytes of eMLC NAND flash memory for read caching, as well as 8 megabytes of non-volatile NVRAM for write caching. Recall that eMLC memory has a several times higher resource in terms of the number of rewriting cycles compared to MLC memory, it is already actively used in SSD-drives for server use. TurboBoost technology can be compared with SSD caching in SAS RAID controllers, however, unlike the latter, it is completely independent from other components of the disk subsystem - the TurboBoost drive does not require the installation of additional software or the use of special equipment.
')
As specific examples, consider two models - ST1800MM0088 and ST600MX0052. Both drives are made in the traditional form factor - a 2.5-inch case with a height of 15 mm, and support the SAS3 interface (12 Gbit / s). Model ST1800MM0088 is available with a volume of 1.8 terabytes, with 4 plates, 8 heads and a spindle speed of 10 thousand revolutions per minute. Model ST600MX0052 has a smaller volume - 600 gigabytes (3 plates, 6 heads) at a spindle speed of 15 thousand revolutions per minute. Both drives come with a cache of 128 megabytes, as well as 32 gigabytes of eMLC NAND memory. The manufacturer declared the following performance parameters: for ST600MX0052 - sequential access 180–246 Mb / s, with an average delay level of 2 milliseconds, and for ST1800MM0088 - sequential access 117–241 MB / s, with an average delay level of 2.9 milliseconds.
Seagate ST1800MM0088
Seagate ST600MX0052
Testing * showed the following features of these disks:
- 15-fold performance boost (random access, 100% read)
- 60% performance boost (random access, 65% read, 35% write)
- 15% increase (random access, 35% read, 65% write)
* Indicated performance gain for disk ST600MX0052 (600 GB, 15 thousand rpm) when filling the cache. Additional test parameters: block - 4096 bytes, queue depth - 32, FIO 2.1.14.
Drive Seagate ST600MX0052. Increased performance of random access by small blocks when filling the cache.
In general, Seagate Enterprise Performance hybrid drives with TurboBoost technology can be used in mission-critical server systems and storage systems as a replacement for conventional hard drives. With a suitable load (random access in small blocks, preferential read), they can provide significant performance gains without the need to implement separate SSD caching technologies.
The text was prepared based on materials from the True System company.
Source: https://habr.com/ru/post/392709/
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